I just got the Crown XLi 1500 in today and set up with the Marantz as a pre-amp. I have to say it is quite a significant improvement for this application over the built in power amp in the Marantz. The extra power and current from the Crown seems to really add a lot more control over the mid and low end of the Magnepan speakers and definitely has the ability to drive them to much higher output.
I learned a bit about pairing the preamp to the power amp during this exercise and think this is a really great pairing for the cost of the Crown amp. The Marantz is rated for 0.4v on the pre-amp outputs while the new Crown amps have the ability to switch the impedance rating from 1.4v to 0.775v which is a new feature included on the XLi series so that it is more compatible with consumer products. The 0.775v setting makes for a nice pairing with my system. It still allows me to reasonably amplify the signal to around 300 w per channel at 4 ohms into the Magnepans (not the full 450 w per channel into 4 ohms if I was able to deliver the 0.775v input signal), which is really more than enough. Not looking to kill my hearing before I'm 40.
The benefit here seems to be that the Crown still has a lot of head room over this limit so it is not likely that the Crown will clip (though the pre-amp in the Marantz may if driven too hard). I'm just getting generally good, clean power and sound while it is producing a pretty good stereo image and fairly detailed sound stage. I think this one is a keeper for my system at least for a while. I think the low end could be a bit more defined and separated on this amp, but is it terrible? Not at all. Would I like more detailed low end? Of course..... but is the difference worth the added cost of a true audiophile grade amplifier (easily costing 10 times as much)? Probably not to me. Maybe my tastes will change after I get my mortgage paid off and am no longer paying $1,000 a month on student loans. LOL.
Most importantly, now I feel a lot more comfortable turning up the amp and letting the Magnepans show me what they are really capable of. I think for $250 speakers, $300 power amp, $250 for a pair of Audioquest Type 4 speaker cables and a few other Audioquest RCA interconnects and throwing in the Marantz to tie it all together on the front end, it is a really good system for maybe a total of less than $2,000 (including the Marantz). It isn't bad. And to steal a quote from someone on another thread, "While this may not be the absolute best system or sound, I'm not exactly punishing myself listening to it." LOL.
Thanks for the feed back on this post.