Single coils hum a bit, so I wouldn't worry too much about it. Of course, if it's really bad (which is impossible for me to say), it could be a wiring issue. Your Hartke is likely fine. Is the Hartke adequate? That is totally up to you and what you're looking for in your sound.
I have an Orange Crush 25 combo for when my Ampeg is unnecessary. It is only 25 watts but can easily handle all my basses with some EQ'ing, and is plenty for a bedroom. If you want to up your amp to a 50 watt due to your own reasons, go for it. Go try them out at a music store, try to match what you hear in your head to what you hear in the amp and pick what's best for your sound. Rest assured, 50 watts is plenty for a bedroom, but it will start to lag when playing with others....unless you're in an acoustic situation or something.
I'd throw out a budget and an approximation of what sound you want from an amp if you'd like some suggestions for a combo amp. Amp brands are colored differently (even different models of the same brand), so we all tend to gravitate towards certain brands and models.