The ellusive SAS Expander

Hi there

I have been searching high and low for SAS expander technology for a DIY external DAS RAID enclosure. .

I have an Adaptec 5085 (8 external ports) SAS/SATA controller, 6 15K SAS HDD's and 2 velociraptors enclosed in external HDD frames connected to a PSU via a switch and to the 5085.

I guess my inital idea was to save money however I have to admit, the costs seemed to have blown out- I'm too scared to add it all up these days. Anywho- I have a dozen more SATA and SAS HDD's coming shortly and it would be great if I could connect them to the 5085 for a faster / larger RAID. Chenbro make expander cards that fit into any PCI slot but they advise me that they are not compatible with 5085, just the 5xx45 5 digit models. PMC-Siera advise their cards are only good for JBOD (without some re-engineering and BIOS code being written)- way over my head!! LSI seem to be the leaders in expanders but they don't have complete expander cards that you can simply plug in, configure and off you go with an extra 24 or so SAS ports...

I guess what I'm after is a solution to this- I have 8 ports but I want more, many more, depending on the cost, I'd love 12 more. I don't have any more PCIe slots left and don't want to add any more RAID controllers anyway (I already have 2 SATA RAID's in PCIx slots and the 5085 in a PCIe slot). The only solution I've come up with so far is the Supermicro M28E mobile rack. An eclosure for 8 2.5 inch HDD's that fits into 2 5.25 bays. It has an expander and you can cascade them several times. A product that provides for this infrastructure without the backplane etc would be awesome!

Does anyone know of a SAS expander card compatible with Adaptec 5085?
Kind regards
UncleGuru

P.S. Apologies for my lengthy rambling explanation of my problem...