Hi Kham,
A bit long, so apologies for that. But FWIW, I've been around this block a few times, for a variety of amps I've had, and so have a definite opinion on tubes
Tube selection is highly subjective given our own personal ideas of what "sounds good" and equally the fact that every amp responds differently from even the exact same tubes. The Mesa tubes are, IMHO, a good starting point and, sometimes, yield the tone you want. In other words, you could spend lots of dough on those magic NOS tubes everyone raves about and find yourself coming back to the Boogie ones.
Or not. There are also some serious tonal differences (some would call those "improvements"
) that can be had out there by not only changing to diff tubes, but also diff tube *types.* And to make things even more confusing, each tube will behave differently in each tube position, so a "killer tube" in V1 may sound worse than stock in V2. Bottom line is don't buy into the "you gotta try this killer tube" hype ...could indeed be great, but not for your amp or even your ears.
If I were you, I'd ask yourself what is your amp sound lacking? What would you want to change if you had magic eq beyond your tone knobs? Approach it that way, then ask a GOOD tube vendor who knows what his stock does in a variety of different amps. So while you think you are paying for for the same tube you could have gotten cheaper on ebay (BTDT, don't do it), you're actually paying for a reliable tube, of which the vendor will stand behind, AND his expert guidance in trying to "hear" the sound you've got in your head and recommending tube x, y, or not z.
Sorry for the long-winded reply, but tubes are all too often bandied around as tonal panaceas ("we all know those just rock in my amp dude"), or even blamed because "everyone knows those tubes suck." They are another factor in a line of electronic components that *influence* the shape and dynamics of your tone ..."how" they influence and how much varies as much as there are opinions on these boards. Hope this helps.
...oh, sorry. Forgot to recommend a tube guy. Mike at KCA tubes is excellent. No affiliation here except a happy customer after many less-than-satisfying experiences elsewhere.
http://www.kcanostubes.com/content/
Edward