Information Overload

Maybe some of you fine folks could help lead me in the right direction. I need help choosing the right DIY build.
I'm looking for plans. I don't need a flat pack or anything. I can take care of the woodworking.
I have a budget of around $600.
I have a large, open room that's not the best, it's a bit reverb-y.
I'm using a Marantz HT receiver.
Although this is the beginning of my audiophile journey, I've been a professional musician/music lover my entire life and spent a lot of time in studios/stages.
I used to build SQ car audio systems.
I'd really like a floorstander, if possible.
My #1 main concern is fidelity, accuracy, detail, soundstage, clarity, etc.
I will be running a subwoofer so it doesn't matter about subterranean bass.