Looking to upgrade my preamp - suggestions?

My system has been coming along pretty nicely since I started putting it together 2 years ago and I am now thinking about upgrading to a better preamp. I'm looking for opinions about which preamp would go well with my Manley 300b neoclassic amps. The Manleys only have RCA inputs (no balanced inputs).

Here are the amp specs:
http://www.manleylabs.com/containerpages/seppneo.html#specs

I am currently using the Manley Shrimp, which I still think is a good unit for the $$$. I'd like to upgrade however because I think a better preamp would improve the bass, give me a bigger soundstange and also improve my ability to hear further into the music. My system now is a bit laid back - many recordings sound like they are coming from a few feet behind the speakers. I would like a bit more forward presentation. The sound is rather neutral which I like. Not looking for an artificially warm tube sound.

I would like to buy in the used market and I'm fairly flexible on price range - $2000-$3000 or so. I would love to own a Conrad Johnson CT5 (or Ref 3) but at $4500 or so (used) its a rather outsized investment relative to other components in my system. I really built my system around the 300b amps :) In my opinion, past $3k on a preamp I would be better served upgrading my speakers?