It seems like them did one run of those and then never got them back in stock. Which is kind of a shame because it seemed like they might be a very good setup.
Short answer I would say check out:
- ST (made by KW)
- BC racing
- KW V1
These will probably be out of your price range, but you may want to double check
- KW V2
- Ground Control (their website says m5 only, but I know 540 guys have bought setups from them. I think they can do I6 versions too, they would just need to use different spring rates)
- TC Klein
Long answer:
If you want adjustable dampening people seem to be happy with BC racing although as far as longevity I don't think they have been around that long. If you do get them I think everyone recommends the Koyo bearings (as there were complaints about the normal bearings I don't remember what they were). The Koyo may now be the default option from Tristan at circuit motorsports who I think is the preferred/ forum popular source for forum members for BC coil overs.
http://www.circuitmotorsports.net/
KW has a very good reputation, but you do pay for them and the V1s don't have dampening adjustment. I think if you step up to the V2s to get adjustable dampening they are going to be similarly priced to the PSS9s so probably out of your price range.
STs are made by KW and are galvanized steel versus the KWs stainless steel. I think the STs might actually be identical to KW V1s except for the different materials used to keep costs down hence the lower price than KW V1s. If you run your car in the winter the KWs might be a slightly better option.
I'm not sure how knowledgeable you are with suspension set ups, but reading through this thread may be helpful. Especially DHoang's comments he always does a really good job describing things so even someone like me who does not know a ton about the technical side of how suspensions work can understand them.
http://forums.bimmerforums.com/forum/showthread.php?t=1804527&highlight=coil+over