Which used preamp for Halo A21, under $1,000?

I used this YS audio tube preamp with my Parasound a21 and it softened up the sound just beautifully. images just float in the air. Very clean sounding preamp. You will need to change the stock tubes out.
http://www.ys-audio.com/sp+.htm

Parasound just released a new pre amp, the P5. If anything would sound good with a Parasound amp, you'd think a Parasound pre would.

Mechans: I'm open to SS and tubes.

Czarivey: I'll keep an eye out for the Muse Model 3.

Daniel825: I was reading about the YS pre last night. Do you still run it with the A21? If not, what did you replace it with and why?

Runnin: I've thought about the P5, but I'm waiting for some reviews to trickle in.

I was surprised by the YS audio preamps The prices were very reasonable. It appeared to be a 12AX7 design (not sure), I wondered which tubes needed to be changed. Although I put old stock tubes in my gear where ever it makes sense.

Daniel825 and Mechans: Which YS Audio preamps have you both used? I see there are a few different models.