Does it matter what power amp i get?

Of course, practically any amp "will work" and make sound come out.

It is a matter of how much sound quality you want.

There are amps which could cost from $50 to $50,000 and what you are probably looking for is somewhere in the middle. Pick a budget, and look for some good reviews and online comments about amps in the price range, and hopefully using the same speakers as you have(or similar).

Not all amps are created equal, and getting a really good one that matches your speakers well, in your budget, will take a little time and effort to determine.

depends it you want decent sound or not...what is your budget? What are the ratings of these speakers (ohms, resistance)?

Oh Ok, I thought the power amp simply powered the speakers, How can it affect sound quality?

Some things about amps definitely matter. You want an amp that can deliver the power your speakers demand. That's a function of their sensitivity and the impedance load they present. Every 100w amp isn't the same, because not every 100w amp can deliver those 100w with low distortion, and because not every 100w amp can handle sudden bursts of power or drops in speaker impedance.

Beyond that, however, amps are fairly similar. The best test is to get an amp into your system and see how it sounds--or, to be more precise, how your system sounds with that amp. Turn the volume up as high as you normally would, and see if you can detect any strain or distortion. If not, then that amp is probably good enough for your needs.

driley, everything up the chain from the speakers affect the sound coming out. Amps, like other components, do have different characteristics from one another. Twl hit the nail on the head when he suggested you take care to match the amp to the speakers. Some amps that sound fine with one speaker will not sound so fine with another (e.g., different damping characteristics or input impedences).

Generally, manufactures match amps to their speakers, so if you are looking at the same brand of amp as are your speakers, you should be OK. Try the Alesis -- if you're happy, go for it. I imagine you should be able to get some kind of money back guarantee you can use if you are unhappy. What the heck -- try a side by side comparison with another amp (also with a good return policy) and see which rocks your boat. Good luck.