Stereo preamp upgrade


Hello! I was hoping to get some advice from the last true audiophiles. Some time ago I purchased my first separates system after my college roommate got me into home audio. The system consists of a Rotel RC-1070 preamp, Rotel RB-1080 amp, Paradigm Studio Monitor 100 v2's, with Tara Labs and AQ power cords and IC's. Something isn't "right" with my system. I'm pretty sure it's my preamp.

I've had a great opportunity to hear a LOT of equipment, since my aforementioned roommate was a repair tech at a local hi-fi shop. He would bring really nice gear home constantly and we would audition his repair work, not to mention the equipment at the store. He had the same speakers as I have now so I know how they can sound.

The Rotel preamp is decent but the bass is not 'warm & soothing,' but has more of a raw feel. It seems to be tight and controlled, likely due to the amp, but it just doesn't seem to have that 'earthy' feel if that makes sense. The soundstage could be improved. It seems wide enough, given my crappy apartment acoustics, but the depth just isn't there. There is no 3rd dimension. Tonality is great. It's not dark or overly bright.

So, I'm looking for a recommendation for a new preamp. I only want a stereo preamp. I would love to have one with a optical input, but I suppose I could get a DAC instead (that's a whole 'nother subject), as I've begun to use a computer to play .flac's. I'm looking to spend around $500 and don't mind if it's used. I've considered the Adcom GFP-750 as I know it's a solid unit, but I don't have much experience in preamps.

What would you do in my position? Music comes first.
chips_n_hotsauce
If you can get by without analog inputs, get a used Benchmark DAC-1, run its balanced outputs into the power amp and use the Benchmark's volume control. And you get a free headphone amp out of the deal. Experiment with the gain jumpers.
Thanks again for the rec's. This unit can use EF91, 92, & 95. I received some driver tubes today, a matched pair of Voshkod 6ZH1P-EV. I still want to get my hands on the Mullard M8100's, as I have a good idea of what they will sound like (nice!). I'm burning the Voshkod's in atm, and so far they sound pretty good. A little bright up top, but after burn-in they should calm down a bit. I'll experiment with the LDMKIV for a bit before I make a decision. If it works out, I may use it for music and the Rotel for movies. I have some power tubes coming as well.

I did want to run the idea of a DAC past you guys while I check up on your recommendations. What's your opinion on the Schiit Bifrost?
supposed to have a really good USB implementation, uses separate crystal oscillators for 44.1 and 48 kHz signals and their multiples, which avoids the creation of jitter in upconverting the 44.1 kHz signals, but reviews have stated that it sounds a bit more lean/bright/detailed than other more expensive offerings. I have not heard one, but it came down to the Bifrost or the Digital Link III, I went with the DL III. I use a Vlink with it, and I think the DL III sounds bright in my system. I am considering upgrading the speakers or the converter, might also toss in a Bifrost with a 30 day trial, just to see what happens...YMMV...