Infinity Renaissance 90

I have to 2nd your observation.  Bought mine around 2000 and then a spare pair of EMIT's from Infinity just in case, then a spare pair of 90's just in case.  Only thing I have done is replace the foam in the rear port and wax them a few times. 
Powered with a Krell 300cx & KCT pre, I am in bliss.  They are an amazing asset to my system. 
Good luck with your power change.  Should be fun indeed.
-John

I love the Ren 90's, the best I heard them was bi-amped with two big solid state Krells. 

The Ren 90’s have a load presented to the amp very much like the Kappa 9’s (I was told by Trevor who measured this graph linked below).

Saying that to get the very best out of them, your Krell on the bottom is the right amp to drive that low impedance, but I think the upper mids around 5khz which is the same kind of nasty load as the low bass, and maybe an amp more like the Krell (a current pusher), only smaller (as you wouldn’t need 400w) would do better up there also for the mids and highs.
http://www.rageaudio.com.au/modules/gallery/albums/Kappa9/img/090801082656_kappa9.jpg

Cheers George

Any suggestions on placement, tilt? Also any idea if the grills need to be left on to sound right?

I agree with you 100% I liked mine so much I upgraded to the epsilon.

The epsilon sounds a little better than the Ren 90’s but at a much higher cost, the two speakers sound very similar but the epsilon bass is more tuneful, the mid bass is quicker and high the frequencies have a little more sparkle, other than that they really do sound very similar.

One other thing I noticed was the epsilon really needs a big room to sound their best, the Ren 90 on the other hand I have used with great success in a much smaller room.

So for the price you can get a used pair of Ren 90’s for, to me they win.