The Problem: I regularly commute 18 miles over some rough roads and lately I've been breaking spokes or having spokes loosen up severely almost every ride. I weigh 210lbs and with all my gear & laptop, clothes, etc. on the rear panniers it must get close to 240-250 some days. I ride a decent Bianchi (Castro Valley with several mods), the rear wheel is 32 spoke-count on a Tiagra 4500 hub. 130mm rear spacing, I believe.
The LBS Diagnosis: So, the current rear hub seems to be of "meh" quality -- i.e. not worth rebuilding a wheel around, according to LBS guys. Also, the spokes have already been replaced on a replacement rim once (got hit by a car on my bike's maiden voyage, long story). So, opting for a new wheel seems the way to go. They're quoting me $90 for a Sta-True Double-Wall wheel.
My Question/Solicitation of Advice: I really, really need to stay on a tight budget here and "performance" isn't my primary goal, but rather durability and dependability is (and if we can avoid the heaviest wheels on the planet, that's a bonus). Should I opt for a 36 spoke count wheel? Any suggestions for good rims, hubs, spokes, etc.? What are the "musts" when asking a rear wheel to carry 250-ish lbs on crummy roads roughly 100 miles per week? I'm looking to stay within $75-$125 or some shouting distance thereof.