Yes, I can offer a suggestion. As you already know, speaker preference is just that. A preference. There are a lot of very good and not so good speakers, and you will get dozens upon dozens of choices to sort through. I'll leave that to others to suggest and for you to audition.
Your great room is a large volume area and is no doubt open to other areas. If so, then you are talking about an "extreme" room size, which doesn't bode well for the word "budget". One has to be realistic on what is trying to be accomplished here. Will $600 get you a pair of good bookshelf speakers? Yes, provided you don't place them on bookshelves. Will $600 give you a good 5-speaker setup? No. And we haven't mentioned the receiver and the subwoofer. I think you are trying to fill a cathedral with a thimble, so my suggestion is to wait until decent funds (two grand minimum) are available before adding a surround system with a subwoofer that has any hope of filling such a volume size.
While you may not like my answer, you'll thank me later if you heed the advice.