I think I already know the answer to this one but I just need some fellow roadies to verify my concern and tell me to pony up the money and stop being such a cheap skate.

My bike came with Shimano WH-R500 wheels in a 20/24 spoke configuration. I was so concerned with getting good drivetrain components when I bought the bike, I never thought to ensure the wheels were quality.

They got me through a few hundred base miles just fine (surely better than my 25 year old bike that I used to ride!). But earlier this month, the rear wheel just felt completely out of whack. Brought the bike in for a tune up, had the wheels trued, and things seemed good again. Then just a week or two after the trueing, the rear wheel just felt sloppy again. I have no experience with spokes, but comparing the front wheel to the rear wheel there is noticeable difference in tension, worse on the drivetrain side. So far, I have not broken a spoke but a quick search online suggests that this wheel starts to completely fall apart at 2k miles or so. I am about 1/3 the way there.

Down to 212 lbs (woo! down almost 15lbs so far this spring)... I am still damn heavy and the consensus online seems to be someone my weight needs to have at least 32 spokes in the rear for a traditional wheel. I am pusher and not a spinner and can really go after the pedals pretty hard which is often when the wheel feels its worst, sliding around under me. When I stand up and pedal hard while tilting the bike over, it feels really unstable in the rear. Could just be sloppy technique.

So I need some justification for spending a few hundred bucks on a wheelset after having only recently purchased the bike. My biggest concern is stability and strength under my heavy frame and my lack of skill, mashing the pedals and all. The roads around here are mostly in really good condition and I almost never hit pot holes, mostly concerned about my own weight and how the rear wheel performs under weight. Recommendations?