Not really, Skuzzy... OEM = Original Equipment Manufacturer - these are cards that are sold to systems integrators to put into computers that they are building, so they don't have the fancy box, and are probably missing some of the software extras (such as bundled games if they come with the retail version.) I believe white box refers to the same cards.
The Radeon 8500 is currently the cream of the ATI crop, and benchmarks higher than most GF3s. It would be very, very worth it to spend the extra $30, though at that price, I suspect you are looking at a Radeon 8500 LE, which is clocked down a bit, kind of like a Ti 200 vs. a Ti 500. Whatever you are going to buy, make sure you read the complete product description on the site you are going to buy from (I recommend newegg.com - they have most stuff for cheaper than most other places, and will get it to you very quickly), and compare that to the chip manufacturer spec to make sure you know exactly what you are getting. A site like newegg will have links to reviews of the exact model you are looking at in most cases.
For $160, you could get the Gainward GF3 Ti 200 I just bought (which has me changing my pants regularly).
What are you currently running?