I'm not a big tube fan (to each their own), but I use a Pass Labs X2.5 as my analog preamp, downstream from my 950.

The Pass and the 950 are not in the same playing field as far as 2-channel analog goes. I was shocked by the increase in dynamics, soundstage width and height and especially bass impact and depth when I put the Pass into the system.

That said, it's important to note that using two preamps can cause some significant headaches if you don't have full-range front speakers (luckily I do) and need to integrate a subwoofer(s). You'd need to either:
a) build or buy some sort of switchable crossover
or
b) have an active crossover and dedicated 2-channel subwoofer(s) and dedicated HT subwoofer(s).

Shouldn't be an issue w/ your 100s though, as you could just run them full-range from the analog preamp and crossed-over from the 950.

BTW, I did notice an improvement in HT bass by going this route. I previously set the crossovers in the 950 to either run the fronts full-range or crossed at 40hz, the center crossed at 60hz and the other speakers crossed at 80hz. I now run everything crossed at 60hz in the 950 and there seems to be a touch smoother. Probably less cancellation going on.


[This message has been edited by jgubman (edited September 16, 2004).]