Thanks for the input dr croubie. I use a local company http://www.posterjack.ca for all my printing and they seem to do a real good job. They offer a 20x30 print on glossy photo paper for $19.99. So by that logic asking for something in the $40 to $60 range would be fair.I think pearl or lustre would suit your image though, while glossy would kill it.
I should really look into getting a decent quality photo printer for quality test prints, but for now i suppose this is a viable option.
+1 I have a large format epson too and I find lustre to work well with a lot of images, especially when people have seen the image on a computer screen. Matt images can sometime seem a bit dull if your used to looking at images from a screen all day, whilst glossy can be too far the other way.
I'm not knocking the other papers at all, as different images work better with different paper types [one of my fav prints is on matt paper] but just stating lustre/semi gloss is probably going to be the safest bet for you.