First, you have to decide what type of longer armed quilting you would like to do and have. For example, is a stretched machine OK? If so, then the Bailey, WoW, Voyager, etc. fit that bill and in a reasonable price range. All have good and bad points, people who like them and people who don't. generally <5,000
Would you like to go up to a little more machine with more of a commercial grade parts and smoother quilting and more features? If so, there are many differences here. Some come with a stitch regulator standard, others it's an add on. Do read the details to determine what is additional cost, and what comes with the machine. You'll need to decide what you need/want for your quilting, and how much quilting you'll really do. These are heavier duty cast commercial parts and are not stretched sewing machine parts. The needle speed is also faster. generally <10,000
Do you want to go into business or want more machine? If so, then consider even one of the more expensive machines, with the appropriate maintenance schedule, oiling, etc. and of course, the steeper price tags. These are commercial machines. >10,000-40,000
I think for most of these you could purchase some type of computer system if you desire that. It's additional :)
I did all my research online, looking at the cost and determining what features were most important to me. I read up on all of them to make sure I understood what they were used for, and who had them. Then I began seriously shopping, and that included contacting the companies for pamplets/DVD's, trials on existing machines in my area, a trip to Houston and I made a chart to compare features, including pricing and what came standard (this is important and can significantly raise your cost...and some machines don't even come with handles or lights!). This takes time, but it's how you can assure you won't be sorry for your purchase.
In the end, I determined a HQ fit my needs. It came with every option I desired already included. A 4-pole frame (wouldn't have a 3 pole system), stitch regulator, one stitch, 1/2 stitch, slow/fast speed controls on handles, needle up/down, 1,600 SPM, larger M bobbins, local dealer, wonderful tech support, low mtc., all controls on handles not elsewhere, ergonomically correct handles (very important to me),etc. It works beautifully for me and my needs. Just perfect! One thing that was very important to me was the maintenance schedule. During my reading I discovered some machines require daily, weekly, semi-weekly, monthly, quarterly and semi-annual maintenances of varying degrees. I wanted nothing to do with all that oiling, leaking of oil, wiring, soldering, etc. One drop every other bobbin change seamed reasonable.
And finally, you have to decide how much you're willing to spend. Would you consider a good used machine (many bargains out there right now!). In addition to the machine, you will have large thread costs, templates, ruler base (you will want this), and training classes, DVD's, and books. These add up. (My DH just shakes his head when he looks in my room! LOL!)
So...you just have to decide. What is important to you? Everyone loves their own brand. Very few will admist to any shortcomings. They all have them. Do do your research online, narrow down some things, and then follow your heart/budget. I love my machine, and I never thought anything would take the place of piecing...until I got into longarming. Now I'd rather longarm than anything else. I choose well for me. I do tons of charity work for our soldiers and then myself...and I keep a backlog :)
Good luck in your search. There's a lot of very good machines/frames out there. (OH! Didn't mention frames, but they are VERY important. A poor,wobbly frame can ruin your quilting experience and make it hard to quilt. Don't underestimate the need for a good one, and you'll be happiest with one that can change length if you are short on space. I know mine is awesome, and I'm so glad I decided I must have a 4-pole. (Research to find out the difference!)
Good luck!