What are the best tubes for a Mesa Boogie 400+, tone wise?

[seventhsunbass]

I am picking up my new addition Weds., a Mesa 400+ and wanted to ask what tubes would be best? Not really looking for a bunch of overdrive and grit, more a smooth blues with a good mid. I sold my Ampeg SVT-300 to finance this C-list buy. Liked it but needed a Boogie as I have the Mpulse 600 and cabinet assortment already. Plus I have wanted one of these for years and luck smiled on me.
I have an array of Leo Fender era basses (one of each) for an idea of my input to the amp.

Eons ago I had, IMHO, the best sounding amp ever, the 90 watt Traynor YBA 1-A (two 6CA7s). I used Groove Tubes to replace some GE's in it and it was perfect for the garage, grungy, nasty sound I wanted but could also be smooth and ballsy. Please let me know your experience with your own 400+ and the tubes you chose.

Also, what you hear as to the difference in pre-amp tubes (12ax7, 12au7, etc...)?

Thanks ahead of tyme for the help of the TB sages. SSB

[ridgeback]

for me i have always used the standard mesa tubes..never needed to change anything.does everything i want so what more can i say....enjoy

[RickenBoogie]

If the tubes are working in the Mesa, there's no reason to change them. IF you decide to change them, it's completely subjective as to which or what tubes your ears would like best.