Adam, mats are kind of a personal preference. And they really don't make or break a turntable. The problem is, you could end up spending $300 or $400 trying different mats and that's money you could have spent on a cartridge.
Step 1: Get the glass platter. Enjoy the table for awhile. Change only one thing at a time so you can listen and evaluate with just one variable.
Step 2: Happy? Stop. Unhappy? Call a good dealer like Needle Doctor or Music Direct or Elusive Disc and tell them what you don't like and ask if a mat may alleviate it.
I love Gadfly's idea of using the $5 cork dots. Compare the felt mat to the cork dots AFTER you spend some time with the glass platter.
I will say this: I don't like acrylic platers. The ones I've tried, compared with glass or MDF or even metal, sound wrong to me though tables designed from the ground up to use an acrylic platter don't suffer as much. Your mileage may vary. Rega designed your table to be used with glass. They switched to MDF because NAD needed to bring the 533 in at a certain price point. Consider that when making your decision.
