I had similar fears. I'd struggled for 7 years with a Janome that was a bit of a lemon - great for piecing but rubbish for quilting - and eventually decided I'd have to replace it or find a new hobby. It became obvious that I was going to have to make a major purchase - very scary when you're on a pension. I started off by saying "anything but a Janome", but several months of reading reviews and forums and trying out other machines brought me to the conclusion that it might be the best choice. I assumed I'd go for a 6600 - the 7700 just looked so big and scary, and was beyond my budget. But continued reading seemed to suggest that it was currently the best machine out there for quilting and the large harp space certainly appealed. A good offer on the price in January of this year clinched it. I had several sleepless nights - it seemed such a lot of money to spend, even with the offer, and I was so scared that I'd not be able to cope with it or would still have problems with quilting (both Janome and my old dealer insisted they were my fault, not the machine's). But when I went and tried it out, I was thrilled: being used to a Janome, it seemed very familiar, in spite of being so much more sophisticated, and guess what - suddenly I could quilt! 2 months later I'm still very, very happy. Even if I never used any of its other features (which I will with time), it would be worth every penny for me, because I can just sit down and quilt, and not spend all my time and energy fighting the machine.
So I would say above all take your time, join forums for the machines you're interested in and ask questions, ask everyone you know what they think of their machines, try different ones, make sure you find a helpful dealer who will let you spend a lot of time on the machines you're considering. Maybe consider the cheaper alternatives - I looked at vintage machines and cheaper models to see if they would do what I was looking for and only moved back to looking at the high-end machines when I was pretty sure they wouldn't. Hopefully you'll gradually find it becomes clearer what you need and what you'd be comfortable with.