Avatar SE Tubes

Can anyone recommend tubes for the Avatar SE that will increase 3 dimensional sound and possibly slight midrange bloom? It currently has the stock tubes and I'm wondering which direction to go. The stock tubes sound great but you understand...

I'm interested in NOS tubes as well as current models but am looking at spending maybe $300-$400 without phono changes. I'm sure this limits my choices but any advice very welcomed. Which tubes are most important to start with?

I bought an Avatar SE that came with NOS tubes. National Electric (Siemens) EL-34s and Mullard CV4003 (12AU7) and CV4004 (12AX7).

You might want to try the National Electric/Siemens EL-34s. Will probably cost about $250 for the set. The Mullard CV4003s will set you back about a $125 or so and will definitely add some mid-range bloom. They tend to be a little warm versus say the equivalent in Telefunkens. RCA 12AU7s (chrome domes) could be another option that will help add some bloom as well.

Be sure to get some really nice low noise tubes though. Andy at Vintage Tube Services has always done me right.
Appreciate it Clio09, I'll do some research on these.
I'm still doing some reading on tubes for this amp. Any opinions on Telefunkin, Amperex 12ax7 or Mazda 12au7 tubes in the Avatar? From what I read these are some brands that might strike a chord. Just curious about who has been down this road before I take the $$$ plunge.

Update on the cost. Under $500 is what I am looking at.