I too can recommend the RKE's. Fabulous EPs on my 8" f/4.
For your f/6 dob, there are a couple other very good options that won't break the bank. These are available form Andrews Communications, from the Guan Sheng (GSO) range:
http://andrewscom.com.au/site-section-10.htm
*SuperView 30mm $69
*SuperView 15mm $49
I have used them both on a dob just like yours, and they are superb.
Another EP I can recommend is the TMB Paragon 30mm. Around $300 new (from Frontier Optics). It depends on how much you want to spend. I have both the SuperViews, and I'm happy with them, but the TMB 30mm IS a better EP than the GSO 30mm. The 15mm GSO is in a legue of its own, however.
Mental.