Gary: The way I understand the 10/100 "rule," the preamp output should be around 470 ohms. However, this doesn't mean that, say, the Rogue 66 (650 ohms) wouldn't work out just fine; listening is the key. If you have the funds, it might not be such a bad idea to buy a couple of used preamps on Audiogon and try out each one for a couple of weeks. Most of the common brands are really good: Cary, CJ, VTL, Rogue, etc (reliability really shouldn't be an issue if you're careful--no hot swapping!). Each has its own sound signature. Keep the best one; you can most likely sell the runners-up for about what you paid for them.
What I like about the Aleph 30 and the VTL combo is this: Pass wanted the 30 to be more workable for tube preamps; VTL wanted the 2.5 and 5.5 to be more compatible with ss power amps. Theoretically, this particular combo should be synergistically ideal. Sure, it's theory, but my early applications have been enjoyable. In fact, things are really starting to settle in nicely as I approach about 25 hours of listening time. I think that things will get even better with more listening.
No matter what you try, have fun--avoid frustration. Remember, this is F-U-N. Have a good time experimenting!
John
