Tube Phono-Stage question.

I recently purchased a REGA P5 TT and had a Benz-Micro Glider installed. I have been using a NAD PP2 phono stage with the rest of my gear. I paid about $129 dollars for this phono-stage and was happy with its performance for the price. However, I recently visited my local dealer and he gave me a brand new and unused Pro-Ject Tube Box II to demo. I instantly liked the sound of the tubes! The sound-stage was much larger and wider! Although, after switching back to the NAD I noticed that the bass from the NAD was much more clear than the tube phono stage. I know absolutely nothing about tubes. My question is if the tubes sound will improve over time? Will the bass become more clear and tight over time? Everything else sounds great, but the bass just sounds a wee bit mushy. Given the difference in price I am not sure it is worth the additional investment. The Tube Box II retails for $450 dollars! I want to improve my sound, but am not sure what to do at the moment! I don't really want to spend for than $500 dollars. Thanks for any information or recommendations!

Speakers: Wilson Sophia's Series 1
Amp: Mark Levinson 331
Pre-Amp: Ayre Acoustics K1XE
TT: REGA P5
Cartridge: Benz-Micro Glider
Phono Stage: NAD PP2 (Looking to upgrade)
Current Demo: Pro-Ject Tube Box II (Have been using for about 3 days now)