I'll interpret your use of the word 'printer' to encompass printing by someone else just because I've never been as happy with inkjet prints as i've been with real photo paper prints...
i use adoramapix for 20x30 lustre prints relatively often, as well as some true b&w prints (really b&w paper is only sliiiiiiiiiiiiiightly nicer).
my clients have been very happy with their 20x30s in particular, which I think are usually around $20 but were on special for $12 a while ago...