I have a similar question
Well, to control the sound with the remote would have to be done with the headphone jack. The RCA is a set analog signal that doesn't have an amplifier - the headphone jack, however DOES have an amplifier.
The cable for most 2.1 systems will be the 3.5mm jack, which fits perfectly into the headphone jack.
So the best thing to do would be to go try out some speakers - stereo, or even a 2.1 if you want the extr bass. I might even suggest taking an mp3 player to the store to plug them in and see how they each sound with the volume from the mp3 player at "half volume". That way, as you plug them in, you can hear how strong the amp is in the speakers based on the consistent volume coming from the mp3 player. You'll likely find some speakers that drive the signal better than others.
I honestly don't have any recommendations on speaker brands. I've found that in some cases, the less expensive ones sounded better to me than some of the marketing hype from better known brands, so close your eyes and choose your audio that way.
Let me know if you have any more questions, or would like further consumer tips. We're here to help!