I heartily agree with OregonMouse that if you wish to carry 50+ lbs, as your original post indicated, a frameless pack is NOT the way to go. You will want that much weight distributed efficiently to a padded hip belt and a frameless pack simply cannot accomplish that.

As for spending up to $200, you should be able to get a reasonably capacious and comfortable framed pack (internal or external frame) within that cost limit. The standard advice on buying a pack is 1) buy it only after you have assembled all your gear 2) try it on with all your gear inside, plus the equivalent weight of all the food and water you'd expect to carry 3) if it doesn't fit you excellently and feel comfortable after 15 to 30 minutes of carrying your stuff, there is no way on god's green earth it will feel comfortable after 6 to 8 hours of carrying the same stuff on the trail. So, return it and try again.

As for a good fit, price has little or no correlation to fit. Most mid to high end pack makers make realtively good quality packs, so when making your choice go with fit, fit and fit, not cost.