I see "scancafe" advertised a lot. If you use the code ROCKWELL21AUG11 (from Kenrockwell.com) you get a 21% discount. Are you still shooting E6? If so, have you considered getting a new scanner? The Epson V700/V750 gets good reviews. I'm using a Canonscan 9500F. This works extremely well for medium format and isn't too bad with 35mm. Its discontinued, but you see them cheap on ebay occassionally. The 9500F has FARE, which is a dust and scratch reduction feature.
I'd be curious to hear how you go. My better 35mm scans are probably as good as digital shots, but most aren't quite there. It would be interesting to hear how good professional scans are.
I quit shooting E6 in 2008, but when I look at the scans, the are quite poor. At the time, I has happy with them, they were as good as my D30 (D30 not 30D), but compared to the 5D and 5D2 they look terrible. They were mostly shot with L seriers glass on a 1V (they days when you could buy and hold a body!), so the actual transparancies are quite good (except for low DR), I'd just like to get the digitals to look much better on the computer. What was acceptable in 2002 doesn;t cut it today.
I really don't want to do it myself, It takes too long to scan at the highest resolution. I see scancafe offers them at 0.29/scan + 0.24/scan for TIFF. 500 slides for $300 actually sounds like a good deal. I guess it's time to do some sorting.
Thanks's for the help in identifying a solution!