You'll find 30W amps are more common but in some ways I'd concentrate on speaker size as amp figures can lie (50watt is most common in bass amps). Look for twelve inch speakers that give a clean sound (dirt can always be introduced by a pedal). Peavey Valveking 112 (also two 12" speakers the 212) and Kustom Defender are worth a look and not expensive.
Pedals - if you're getting a decent amp you should be able to dial in a good bit of distortion there so an overdrive pedal isn't the first to get. I'd recommend a Compression pedal as this has a wide range of uses. You may also find a boost pedal useful try one when buying the amp and see if it gives an edge, Electro Harmonix's KO is an interesting variation on this.
If you are in the market for a guitar as well you are in a great position to try out amp/guitar/pedal combinations and drive a shop crazy. Don't decide on one and then match everything to it, keep you mind open and options fluid (store assistants hate this, but do it anyway). So try a single coil with some amps then try out a humbucker guitar with the same amps. Then try pedals with it and see how both react. The treble boost pedals I mentioned behave differently with different amps (must be tube though) and guitars (depends on the tone pot).
Let us know more about the sort of sound you are gravitating towards and we can advise more (if you said metal then I'd recommend humbuckers, a Marshall and a metalzone type pedal, if you said country I'd recommend single coils, Fender amp and a compressor etc.).
'The sound of the city seems to disappear'