Phono Pre Amp?


I am using the little NAD but i want to upgrade, I am using a Music Hall MMF5.

What Pre Amp will make an improvement, that costs under $400.00's or is it not even worth upgrading?

Thanks
128x128thegoldenear
My system is as follows:

Primare I21
Primare CD21
Thiel 1.6
Kimber PBJ from NAD to Primare
Kimber Hero from Primare I21 to CD21
Monster MSeries 2.2
Music Hall MMF5 (i love vinyl so much that this piece will be upgraded at some point in the future)

Thats why the budget is low because I know the NAD is not the best and I know I can improve my sound from the MMF5 but I dont know how for under $400.00.

I will do some poking around for the 640p and see what I come up with, thank you.
The NAD unit is really entry level.. I know you can do better... the Graham Slee mentioned above should do it.
Save a few bucks and splurge for the Juicy Music Tercel II. Tubes baby! I upgraded from a Cambridge 640P and the difference is huge!