Guess no one is going to do the usual list of advice:

Buy the gear first and the pack last - so it fits without leaving so much room in the pack that the load shifts around and puts you off balance, or, without inviting you to stuff... more gear in.

Internal frames without a ton of external doodads are the choice if you are bushwacking. External frames are great to haul loads, don't require as much fitting, and are contraindicated for off trail travel through forested or brushy environs, unless you like grid searching for the gear that's been scraped off your pack.

25+ lbs of load and you are probably better with a framed pack; the semi-framed and frameless packs out there are for folks who have their gear down to the lightest weights.

You do not need "top of the line" in the sense that it's the most expensive or best built pack in the world. You need something that fits, and carries the gear you want to take with you, comfortably, without chafing, soreness or endless shifting of the load - the more years old you are, the more critical it is to get that pack to fit well. Your size and weight do not matter in fit. The distance between your iliac crest and the 5th cervical vertebrae is the key factor in pack sizing. See this page to understand this better.

McHale, by the way, does custom made backpacks and are highly regarded, so would be a closer match to "top of the line" than the mass manufactured stuff at REI. BUT, you do not necessarily need a custom pack to find a comfortable and serviceable pack - I have three packs that I paid 100-150 for (apiece) that work well for the various kinds of trips I take.

Which brings me to the next tip: sometimes the best backpack is two or three backpacks. If you go out in winter, for example, you'll probably want something larger than a three season pack, to accommodate the different gear list you need for cold and snowy trips.

There is not going to be a "best brand" - that depends on where and what you are doing, and what style fits you best. Totally personalized. There are no shortcuts for finding a pack that works for you. Take the Osprey packs Glenn mentioned - for me they are a hideous torture device that dig into my hips and leave me feeling like tenderized steak at the end of a hike. Yet there are lots of people who wear those Osprey packs comfortably for miles.