Difficult to offer suggestions without knowing file format or camcorder model but sounds like you’ve plunked yourself down in the middle of a muddle of competing technology manufacturers (Do you remember Sony Betamax and VHS?)
Off the top of my head…
Safest Bet:
Sony Vegas [Expensive]
Safe Bet:
Adobe [Very expensive]
Crap Shoots:
Roxio, Nero, Corel
There’s a few others, but can’t remember the names. You may encounter problems with all of them, so I’d be looking at their support before buying.
Comments:
--- Optimum would be to get Movie Maker working since you like it (which might be a possibility but can’t offer suggestions without knowing camcorder/file format, operating system and Movie Maker version.) By the way, loss of quality may not be the converter but a limitation in Movie Maker.
--- If you like your software to last and be supported: Corel is busily buying up video editors. I like Corel (used various products for years) but they have a reputation for lousy support. Corel bought Roxio early last year; not sure if they’ll continue it; they’re keeping the product line separate and already have two other video editor lines. So you might upgrade Roxio and find it either gone or consolidated in a year or two.
---You can download a fully functional, 30 day trial version of Corel VideoStudio Pro X5 which claims support for some Sony formats (full version $50 in the box.) Proceed with caution, some Corel products do funky things and there’s lots of people complaining about their support, so if it does something to your system you may have to back out of it on your own.
---Audio is a whole ‘nother problem. …again, can’t offer suggestions, too little info. But Sony sure does love copyright protection.
Edited to Add: I had a nagging little thought in the back of my brain and just did a quick Google. Pinnacle Studio. Used to have a good reputation. Corel bought that last July.