For the guys that didn't like the Avalon 737, did u try switching out the tubes? Just wondering because I got mines from a crackhead for $40 (true story - he thought it was a stereo reciever) with some cheap groove tubes in it and I love it. Although I have little high end experience to compare it to
I did try some tube swapping, but could never get any decent tube saturation tone out of it. My complaint with the unit is that the pre and comp designs were too focused on sound transparency and not enough on coloration. It does not really achieve transparent or clean tone as well as a highend solid state / transformer design, nor does it give you the coloration options of better highend tube gear, and on top of that the EQ never suited my personal tastes.
That being said, it is perhaps the best $40 preamp/EQ/comp of all time!
In the end, it all depends on the sound you are going for... It took me forever tweaking to settle on sounds and even then every track I used it on was rerecorded later through something else. Just not my thing. Don't let it stop you from enjoying it!