You can do whatever you want, however I wouldn't suggest using home theater speakers for trying to get an accurate idea of what's happening in a mix.

They are more designed to make crap sound good, rather than letting here why something sounds crap.

As far as small speakers go, I run KRK RP5s. I won't lie and say that they are great, but for what they are, they work well for me. I would say they take time to learn though, no doubt. I made a lot more bad mixes on them then good ones so far in two years or so.

If you are going to be mixing and mastering in a pro studio don't worry about your home speakers. Just track your keyboards at home without effects and as hot as you can up to about -6db. The speakers aren't going to affect the tracking anyway.

Guys

Pl's pour in your ideas....

Sam

Despite what somebody else here stated, you DO need a decently "honest" speaker to track with. You need to hear any BAD artifacts-hums, buzzes, clipping, etc. before you commit the recording.
Many "home theater" systems are designed to minimize these to make the listening experience "better". You'd also be surprised at just how different synth patches and their effects settings can sound through different speakers. A speaker system like the KRK's are designed to serve you better in this regard.