I'm currently in the market for a new combo amp for practice. I really don't wish to spend more than I have to, but I want something that's good quality as well as powerful enough for my needs. Sure, I can get a 30W practice amp for very little money if I'm just playing alone, but how much power should an amp have when in a practice situation where you want to be heard over drums and other instruments? 50W? 100W? Are there any brands that I should avoid?