Well, recently I have been very very content with my systems and haven't been looking to upgrade anything but rather experiment around with what I already own. In the past six months I picked up a used Cal Audio CL-15 with a variable digital output volume and several used speakers. Last week I decided to take the Cary tube pre out of the loop and use the cd player directly to my Rogue 60 watt tube amp. After listening for a while I decided to stick the Musical Fidelity X10 v3 tube buffer stage between the Cal cd player and the Rogue. The X10 v3 is an output impedance matching circuit which essentially removes any "mismatches" in impendance between source and the final stage. The Cal allows me to control the volume remotely from my Lazyboy chair. Man, this is a sweet and very "uncolored" system to listen to. Very very detailed with no sibilance or harshness whatsoever. Not that the Cary made it harsh.. rather the opposite; it makes the sound warmer. Still very good and just different really rather than better. I have several speakers that I am using in this configuration right now:
SDA CRS+ with upgraded tweets (thanks Hoosier21)
Magneplanar MMGs with upgraded capacitors and inductor coils (same values)
Polk Monitor 10A
Spendor BC1 (20+ year old speakers and still one of my favorites)
Spendor SP1/2 (thanks Russman)
All of these speakers sound great with this setup. Really, almost a speaker for just about anyone here (90% or more for sure). I don't think I can get much better sound without spending a ton more money.
So if you ever get bored or want to try something "different" and can configure a setup similar to this you might just be surprised at the sound you get with no preamp.
1st picture is setup with MMGs. Top to bottom is the Rogue, the X10 v3, and the Cal Audio CL-15. B&K amp on bottom shelf not in use.
2nd picture shows the Spendors. BC1s on the left and their descendants the SP1/2s on the right. These speakers love tube amps and give me a lot of listening enjoyment.