Well, yeah, there's that. Thor even preowned can be costly, ranging from $3K to $4K. But worth every penny though. if you ever got one, you'd quit thinking about other preamps though.
Depending on the sound you want to shoot for, I've heard some CJ preamps which sell new for not much more than $1500 that I wouldn't mind owning.... at that price. new of course. I just can't get used to the switffing sound it makes as the volume increases or decreases.
VTL has some well regarded units you can get in that area.
the thing I've found is this, Keeping things comensurate with one another sure does help. Although a bit aged... your amp went new for what, 6 or 7K? Why then put a 2K or so preamp on it? it's pretty neutral and reflects what it is given... so attaching a very very good source, and as well a preamp will surely aid you sonically.
Were it me... I'd not pitch that wad into another lesser pre if it meant only waiting a few more months or so to have the funds needed to get a better one outright.
The Antique Sound Labs "Flora" got very nice reviews from the mags and people here in the personal reviews section.
Another thought is ARC or AR... I believe they offer pre's with balanced outputs... and of course there's the newer BAT pres which are truly fully balanced, front to back.
Good luck in any case.