Amplifier upgrade for Kef Reference 4c trio

I recently took the leap to make a major upgrade to my living room (17' x 17' x 10') audio quality and jumped on the current KEF promotion to get a trio of Reference 4c as part of a larger 5.2.2 setup that is doing dual duty as an HT and a 2-channel system. I had previously been about to pull the trigger on the Reference 3/Reference 2c set based on some broad-ranging speaker auditions, so I knew what I was getting into from a general sound perspective  Despite the oddity of using what's technically a center channel turned on end, they have been an astonishingly good sound, and I couldn't be happier with what I'm getting from them, from a 2-channel or a HT system perspective. They also look quite attractive in rosewood, if I may say.

The challenge I'm currently having is that I am not sure my current amp, an NAD M27, is going to be up to the task of driving them. The Reference 4c are nominally rated at 8 ohms and 90dB, but their impedance can go as low as 2.9 ohms (per the recent ASR review), and KEF recommends amplifiers with power ratings of 50W - 400W for them. If I understand the rule of thumb math correctly, the amplifier for the front LCR should be in the 240W to 440W range, or greater, and the M27 just can't quite cover that.  With stereo amps, there's a wide range of options, but for driving those 3 channels, this power requirement limits my options.  My equipment space limitations mean I really can't fit more than about 10u of amplifiers, and the WAF for this project does not extend to having monoblocks out on the floor, or anything that has exposed tube amplification. The other major consideration is that I need to keep my amplifier budget under about $13k.  For the two-channel side of things, I'm currently using a Legacy Audio Wavelet preamp/DAC/Crossover and a BlueSound Node connected to the Wavelet's USB in. My AV processor is an Anthem AVM 70 which is feeding the front L/R channels to the Wavelet and the rest directly to the M27 amp. To satisfy providing 7 channels and ensuring the front three have adequate power, these are the options I've identified that can work in my space

  1. Legacy Audio iV3 Ultra paired with either the existing M27 or an iV4
  2. Bryston 21B^3 paired with the M27 (this handily beat out the McIntosh MC303 in a back to back listening test with some Contour 60i speakers, so I've stricken the latter from the list of options)
  3. 3x Benchmark AHB2 as bridged monoblocks paired with the M27
  4. 2x Parasound Halo A51, bi-amping the front LCR and using the remaining 4 channels for the surrounds
  5. 3x PS Audio M700 monoblocks paired with the M27

Have I missed any viable options here?  If so, what might they be?  If not, are there any of these combinations that are likely to significantly outshine the others given the speakers they'd be powering?



Fwiw, I haven’t heard the reference series yet.  But I have r5 (bear with me). I bought my front end based off of auditioning more than a handful of amps with Wilson audio speakers planned on being the reference speaker. While I  couldn’t afford the Wilson’s yet and have been running my new classe delta stereo amp on the r5 with my esoteric CD player.  I personally feel the r series is like a metal dome driver version of newer Wilson’s. I throughly enjoy this modest system a lot. But it meets some of the biggest criteria I have with flying colors.  The classe had the best imaging, natural black background,sturdy weight to the body and overall quality listening with the super transparent Wilson’s. To be sure if we’re on the same page with the kefs, While I love the texture and organic nature of softer drivers, sometimes they give too much texture and simply don’t convey proper timbres.  With the kef r series There’s a step behind in Wilson capability but on the same field with how it presents itself but much more addicting.  There’s something about how kef also enriches the music where sustained notes amber and burn,  with a euphoric energy that I simply never get with the Wilson’s. But like Wilson there’s extra this or that. There’s no overly saturated air with female vocals or instruments that require human lungs to bring themselves to life. Everything is simply where it belongs.  I say all this and only have knowledge of a lesser speaker to yours.  Undoubtedly this is all theory and speculation but if the reference series is as good as I think it is I truly believe the classe stereo is worth looking at. 

I have heard the Delta PRE and Stereo amp paired with some Magico A5 speakers, and it was undoubtedly one of the best stereo amplifiers I have had the opportunity to experience at the price point. Unfortunately, the form factor of that unit poses problems, because it’s only currently available in the monoblock and stereo architectures. Since I need the same power for my center as I do hat my L/R pair, I’d need to purchase 2 Delta amps, and that exceeds the space I have available when you factor in the surround amp I already have. I was hoping to hear about a multichannel offering from Classe at or around CES (heard unsubstantiated rumors that such might be forthcoming), but nothing like that has materialized thus far.

Sorry I was drunk when I wrote this.  It took a long time and this morning I see I did a horrible job. go figure lol.  I hadn’t read your whole post last night either sorry. Are the kef less sensitive than the magicos?  Sensitivity is sensitivity but pretty sure the magicos are a much more demanding speaker.  If they worked in your rig you might not have an issue with the kef.  But if you do, that’s a good list. I’ve never directly compared those so can’t give opinion. 

The A5 are 88dB sensitivity and a nominal impedance of 4 ohms. The Reference 4c are 90dB and a nominal 8-ohm impedance, but the test below indicates that they may be fairly tricky to drive.

An outside party suggested a 3 or 7 channel from the ATI AT6000 family as an option as well, so feedback on that would be helpful too.

I did.  I'm looking to understand if this is more than a 2-channel variant of the M28 successor to my current multi-channel amp.  The testing done at Secrets of Home Theater & Hi-Fi seem to indicate that with an 8-ohm signal, the M28 clips at 275W but starts to distort pretty severely at 185W.  Obviously, the M23 is brand new and doesn't have any outside testing, but if the Purifi Eigentakt modules are unchanged, then I'd expect it to behave similarly.   That said, I could get 3 of them and bridge them as monoblocks like I had considered doing with the AHB2 amps and have power to spare. That would put me in a pretty tight space to get all 4 amps into my equipment space, because I'd still need the M27 to drive the surrounds.

Hi jlotman.  I’ve been considering buying a pair of 4c’s (at their discount price) for a two channel system, and I really like the rosewood finish, which KEF has discontinued.  For the R & L channels, did you just set them directly on the floor?  Seems like they would benefit from using outriggers or perhaps short stands, but I’m a bit stumped on what aftermarket products like this would work best with them.  If you could share your approach, I would appreciate it.

They are currently and temporarily seated in their shipping packaging because I did not want that high-gloss finish on the floor.  A friend of mine who is a professional woodworker is constructing a custom set of 2-piece hollow-base stands with some isoAcoustics Gaia feet for them so they will be lifted, angled, and dampened/isolated properly.  Here's what they currently look like, they still need stain, lacquer, and felt-lining.