best pre-amp new or used for under $500?

Realremo: I recently bought the Anthem gear (TLP 1 and MCA 20 amp) for my dad to replace an older Mac receiver he was using with newer B and W 703 speakers. The pair was a huge improvement, and comes quite close to true high end without breaking the bank. The TLP's contour feature is useful to boost audible bass at lower sound levels.

About where to put money, I would say the speaker and preamp. I tried upgrade my amp, very little difference. I also tried an external DAC, although not a very high end version, also no noticeable difference. But after I upgrade the preamp, I can hear the difference right the way. And of course, the speaker should be the first component to buy in my opinion.

Gte357s - what head unit were you using before you tried an external DAC? And...which DAC, preamp and speakers are you talking about? Agree regarding the amp, I doubt I would be able to hear an audible improvement over my Rotel RB-1080 unless I spent 3x or 4x the money ($1500-$2000). Right now I have to get the pre-amp above the Rotel's level.
Although my Denon 3310 is doing pretty well in my little office. I took down the home theater system and moved it into my office, renovating the living room.
There is a small but insistent contingent of A'gonr's that insist on spending the big $$$ on the head unit first...But how much fun is that?!?

Right now, I am using Sony Blu-ray player, Maverick Audio DAC, Audible Illusions L1 preamp, McCormack DNA-1 Deluxe amp, and B&W CDM9NT speaker.

I had a Rotel CD player before, and then I compare with the cheapy Sony Blu-ray player, can't hear any significant difference. Then I thought the DAC in the Blu-ray player is the weakest link, and I want to go digital to stream music file from my computer, so, I bought Maverick Audio DAC. It is cheap, but reviews are not bad, so just to give a try. I don't think there is much audible improvement comparing to the Blu-ray player. I am not thinking to try out a tube DAC. For the amp, before I upgrade to McCormack, I use Rotel RB-1080. I don't have a chance to do A/B test, but the McCormack is slightly better based on my memory. But again, the improvement is not as big as upgrading the preamp from Rotel to AI.

If you are patient, you will find a Muse 3 @ $500.00. You won't find a Signature 3 at that price, but you won't find a better value than the Muse... Neutral, airy, nice slam and a remote to boot. Do your homework, read the reviews everywhere you can find.
I, like others can say, up your budget, but you'd be hard pressed to beat the Muse 3 for $800.00 to $1000.00 if what you are after is neutral and a remote.