Which tubes? My amp can except El34, 6L6, KT88, an

Creeper, if you wan't to do some reading about the way the powered woofer on the 5 is set up, the review in "The Absolute Sound" explains it quite well. It can be found at the Vandersteen web site. I realize after some reading myself that the Vandersteen 5 comes with the model 5, high pass filter, that goes between your amp and pre-amp.I understand that these are very transparent unlike the crappy little WX-2 supplied as a temporary filter for the 2Wq.

It is my understanding that Vandersteen is offering a upgrade to the Model Fives, there is a change in the subwoofer amplifier, crossover and the midrange driver. The upgrade is around 3800.00 depending on how recent your Fives are. This came from my local dealer after he talked to Richard Vandersteen. There may be other changes as well, I only had the chance to talk with him briefly and probably didn't get all the information.

I can say that the Electro-Harmonix 6550 outperform both the Svetlana 6550 and Svet KT-88 in both my Rogue Tempest, and in the Cary SLI-80 Signature. They sounded cleaner top to bottom. The Svet KT88 had a bit more warmfuzzy in the mids, but you definately heard the fuzzy.
Based on the Super sound of the Electro Harmonix 6550, and the stellar review of their EL-34 in Vacuum Tube Valley, I picked up a matched quad from the the tube store for less than $50...
EL 34 tubes are supposed to have less bass than their big-bottle counterparts, but I gotta say, these things sound GREAT. Note, that my Rogue is auto bias, and is made for the 6550/kt88, so the EL-34 tubes are being run much hotter than is ideal for tube life, which certainly affects sound, but if they sound this good run hard, I can only imagine what they might sound like properly biased.

If you're going to try 6550s, the Svetlanas are super cheap, sound most neutral. I prefer the ElectroHarmonix, and hadn't heard of the aforementioned compatability issues, but I digress. Svetlana KT88s are pretty good, too.
Come to think of it, Svet El34s are cheap and good, too. As I said, I prefer the EH tubes...

HOWEVER
I can't believe, even though you didn't ask for it, that I'm the first one to suggest that the smaller tubes in your amps are much more likely to affect sound quality than the output tubes.

THis thread has pretty much covered the bases, regarding power tubes... what kind of "little tubes" does your amp use???

Kana813, I have been wondering the same thing about the Vandersteen you are talking about, I though it was called the Reference Monitor. We will have to wait and see.

Using a high pass filter before the main amp with the 5's(and with the 2Wq, which I have) gives you the true benifits of bi-amping, since the main amp has the low bass filtered out. Using the speaker signal from the amp lets the built in sub amp take on the character of your main amp so that they don't sound like two distinct and different things, and keeps the blend more seemless. That's why Rec can get away using the amps in triode for 50watts. Same reason I can use a 45 watt amp and the 2Wq with 2Ce's(which are rated at the same 87db sensitivity as the 5)to get fairly realistic levels

Rec, seems the most info that can be found on the update from the Model 5 to the 5A, is in the adds in both the latest Stereophile and TAS. The add states,"a switch-mode power-factor corrected amplifier supply, a proprietary woven-cone midrange with high-efficency magnet assembly,a new tweeter utilizing a more aerodynamic magnet structure and die cast alloy chassis, and the requsite refinements in the crossover.."

Maxgain- agree with the benefits of taking the low bass out
of the main amp. My SF P1SE sound much better(cleaner/faster) without having to deal with the bass from 50 hz down.

I think the V5s are a true classic design that will hold their value(like the other Vandys). I hope Mr.Vandersteen
brings the Signature One/Reference Monitors to market, for those of us who have smaller rooms or want to roll their bass.

Mahalo for all the info.

Aloha & an early Mele Kalikimaka.