You change the length by adjusting how the bowstring hooks up to the cam - has several places to hook it up. At least, that's how it is on my bow.
Nothing bad about any of the bows, actually. Just, that the names I mentioned are considered the Best. I'm not a bow snob....mine cost $40....

.....but there are some things I'm willing to live without.
Now, if I go here, I find that the MSRP for a Parker Phoenix is $619.95 (probably inflated, but what the heck).
http://www.parkerbows.com/phoenix36.html
Hmmmm.... one minute of searching on ebay turns up:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=20838&item=7113881924
Currently around $200 and advertised as Brand New.
So....go to the local shop....pick up all the Parker's....decide which you like best and nab one on ebay. It's not evil....ok, maybe it is....

.....but we all do the same thing with knives....(try in the store, buy online)
Here's a few more tips:
Get the tallest bow that you can hold at draw length for a minute. Longer = more accuracy. Don't fall for the smaller-is-lighter fad that's going around right now.
As has been stated....55 lbs. is plenty. Getting a heavier weight will only make hunting unpleasant because your stamina and accuracy will deteriorate quickly.
Make sure the bow feels well balanced in your hand. When you shoot, the bow will tip forward slightly....this is normal...preferred, actually. So make sure it doesn't feel "back heavy".
You don't need a sight. If you get one anyway....you really only need 2 bars on it. You'll never shoot past 40 yds.....and probably won't need one inside of 10 yds. Set it at 20 yds and at 30 yds and let your eye do the rest.
Get a good arrow rest. Metal is more stiff, but can make noise when you load up your arrow "in the field". A sturdy plastic one is fine.
Get a balancer.
Buy your arrows all at once and have the shop cut them equally and put them together (provided that they are competent...most are).
Ask the guy at the shop to show you proper drawing technique. Really does make all the difference in the world. Of course, his style might not match your own, so get a few different opinions. Should feel natural, not forced.
I do not use a forearm strap and if you shoot right, you shouldn't need one either. Work at it until you get it right.
If you should come upon some spare time....

....there is a pretty good forum on this stuff = archerytalk.com
Be careful, though, there is rampant consumerism on the board.
