Replace Amp or Preamp?

First let me start by saying that im very satisfied with my budget system which currently consist of:
Electron Kinetics Eagle 400 mono blocks
Mcintosh CR10 zone control preamp
Theata data basic/Theata data universal 3 transport
Dunlavy SC4 speakers

I do notice that on some difficult passages I get a little jumble in the music not enough to make me disatisfied but I do notice it from time to time. I have been told by some that the weak point is the CR10 seeing how it is not a true preamp but more of a zone controler. Ive had one person blame it my amps saying that they were good bass amps but thats about all. To each his own but I love the amps as I find them warm and musical.
I have looked at couple preamps but not sure what direction to go thus far im looking at the following:

Audio Experience Symphonies tube preamp
Theata Theta Casablanca

Ive looked at several older Mac preamps but can not bring my self to pay more for a piece of equipment than it cost brand new.

Any suggetions on the 2 preamps mentioned above would be great or any others in the $300 to $500 range that are currently avaliable would be great. For those that think I should be looking at amps as the weak point what do you think of the emotiva XPA-1 amps or any recomendations in the $1000 range?

Thanks
2channeljunkie