I've heard good things about both the Ranchos and the Edelbrocks on Astro vans, heard a complaint or two about monroes and consistency issues in quality such as leaking and shoddily pained ones. Got Gabriels, but then again I got a set off ebay for under $20 shipped. Not too many complaints so far, tons better then the stockers which were dead.
Last year, I installed "KYB Gas-a-Just" on my 1994 4WD K1500 Blazer. They seem alright.
With any high pressure shock (unlike the stock shocks), be prepared for potential annoyance installing them, mainly the front (more cramped working space). The high pressure shocks are normally extended, and it takes quite a lot of force to compress them for install. It's probably because I'm weak
Many people rave about Bilstein shocks, but they're quite a bit more expensive, $60-70 each. Autozone has them.
I bought Bilsteins for the Buick (gently used) and they still work great.
My Trailblazer came with Bilsteins and one of them went bad (from the factory) which was a little strange but replaced under warranty and not a lick of trouble out of 'em since. Also rides and works great!
I had a '92 Jimmy with Monroe's off-road shocks. I liked those a little better then the stock Monroe's. But it seems that all the Monroes I've had wear out quickly.
Ok...I think I will go with Bilsteins but now I have another question. They list two types for my Blazer - heavy duty and sport. The sport are 20 bucks more for the set of 4. Does that mean they are better?
I have the towing package so not sure which ones to get.