I like http://www.tubedepot.com/
. I don't know any tube dealers around town, but I'm fairly new here. I like JJ 6L6GC's for cheapness and quality.
I've built 5-6 amps from scratch using both new and NOS parts. Old NOS 6L6GC tubes are nice, but you'll probably get better tone for your dollar by buying some dependable Chinese or Russian output tubes (like the OEM tubes in your Fender) and then investing some dough instead in a NOS USA-made 12ax7 to go in the V1 position on the amp. This depends on what type of playing you do - if you are driving the output tubes hard, then it might pay off to buy a pair of high-dollar 6L6GC's too. If you use mainly preamp distortion, then 12ax7 is where all your tone is coming from anyway.
I like the idea of buying a matched quad to have spares, but I'm not sure how "matched" the quad will remain when 2 of the tubes have 200 hours and 2 have 0 hours... I've never done a quantitative test of this.
The Hot Rod amps are fixed-bias (a poor choice of words, because bias voltage is adjustable), and therefore need to be re-biased with a new set of tubes. Biasing is really not difficult if you have a multimeter and can read a circuit diagram. http://studentweb.eku.edu/justin_holton/bias_print.html
You can certainly play on your new set of tubes using the previous bias setting (from the old set of tubes) but you won't be optimized for either tone or tube longevity.
Kyle Motor is right, matched preamp tubes are not important, if it's even possible to buy them in matched sets. Preamp tubes work in series, power amp tubes work in parallel, where balance is much more important.