Buying Your First Bass Amp
You will need an bass guitar amplifier of some sort. Again, you will develop unique preferences for different sounding amps once your playing improves. Don’t spend big yet if this is your first amp.
Watts basically describe how powerful the bass amp is. More watts means more power which means more volume. If you are just going to be practicing by yourself at home, you don't need but 20 to 50 watts. If you plan on playing with a guitarist or keyboard player, you may need 200 watts. And if you plan to play in a band with a drummer right away, you need 300-400 watts. You don't want to turn up your bass amp more than 3/4 of the way. It sounds better to have more watts not turned up so much than fewer watts turned all the way up.
You should realize that guitar amps don't need as many watts as bass amps. Bass amps require more power to drive low frequencies. An 80-watt guitar amp can be deafening while an 80-watt bass amp can be hardly heard over a drummer.
Don't be fooled thinking a big speaker means more bass. A good 10-inch speaker can deliver more bass than a cheap 18-inch speaker. Smaller speakers have a punchier sound and bigger speakers have more boominess. A 12-inch or 15-inch speaker should serve you well.
Get a Bass Amp Now!
Don’t wait to buy a bass amp. You need something to hear yourself or you will ruin your bass technique! At least buy something to get going. Without an amp you will compensate by plucking much harder than is required just to hear yourself. This will be hard to correct later on.
Practice hard and save money. When you learn how to play something, go around to all the music stores in town and play every bass and amp you can find. After a while you will begin to notice the subtle differences between various bass guitars and bass amps. Then you can make your own decision based on your newly developed ears, eyes and hands.
I have an even more detailed set of articles about bass amps at my other website. You may want to read those if you're not just buying a small practice amp.
What I Recommend
If you don't have a lot to spend and don't foresee playing gigs anytime soon, a small 20-50 watt practice amp will suffice. Similar to basses, you won't find huge differences in quality among the cheaper practice amps. Hartke, Peavey, Crate, and Fender all make decent practice amps. You probably won't go wrong with any of them.
For larger combo amps, look into amps by Ampeg, Ashdown, Fender, Hartke, Gallien-Kruger, Peavey, Eden, and Line 6. They are all quite good quality.