Thank you! I was concerned with my game having 14 megs of VRAM in one layout which was only half complete, but it looks like I shouldn't worry about it too much anymore.
By testing a game on a lower-end system, how low end do you recommend going? My laptop with integrated graphics can only run it at an average of 15 fps, while my sister's computer which has a Geforce MX4000 (or something like that) get's 60 fps. Should I just ignore the laptop's performance?
Depends on the sort of game you're making, and the type of player you're aiming for. Then anyone with specs below the ones you list as the minimum requirements, aren't supported.
Generally the fancy big sprites and graphics will have a higher minimum spec than the retro style ones using a tiny screen that's zoomed in. Also the lower the minimum specs, the more people will be able to play it. If your game is still playable on your laptop, you could use that as your minimum requirement if you wanted to. It's entirely up to you. So long as you know it works fine on the minimum (even if you've got a lot of effects and such turned off).
The lower the better though, since folk expect 2D games to just work.