I will only relay what I have direct experience with.
I upgraded my bow in spring of 08. Had about same budget as you. I ended up buying a new 07 PSE Brute package for 399.00 of the clearence rack. Added some arrows cut to my length.
I am completely pleased with this bow and was a huge step up from the Wally World bow I bought in 05/06.
Best advice is try as many bows/bow packages (regardless of brand) in the price range you have set for yourself and pick the one that "feels" right to you. Take your time and ask lots and lots of questions about which accessories are best for newbie and your bow that you ultimately select.
Next tidbit, I don't care how much or how little you spend on a bow. Practice, practice, practice, is your best tool in using the bow. Next best thing is more practice, and more practice. Did I mention practice?
I don't use Scent Lok, some of the other members do and can relate their experience, but in bow hunting scent control is very important. How important is a subject of much debate, but one thing is for certain, if a deer gets wind of you the hunt more often than not is over.
Ground or Tree. I do both. I practice, practice, practice, and practice from both. Take your pick you can have success either way. Whichever one you feel most comfortable doing that provides you with the best challenge and most success.
Veni, Vidi, Sagittam Mittere, now I'm ready for my nap