My two standards proofing papers are Epson Enhanced Matte for that end, and Epson Premium Semi-matte for the photo paper.
The semi-matte is only available in rolls though. So Epson Premium Luster is the best choice for the 3800. A very good quality paper, kind of the benchmark for every other paper. It even holds up well when compared to the newer bartya's.
Yes, there are cheaper versions, as you mentioned. Never used them though. I have used a lot of other premium papers, but just stick to my standards for 85% of work.
Best,
Michael