Sorry....I'm not a big proponent of emoticons. Perhaps this:
at the end of my remark might've helped.
I'm not familiar with the iMac's case or internal bus architecture. No PCI bus? No room?
To answer: yes and yes.
An iMac is stuffed into basically the backside of a monitor enclosure. All Power Macs manufactured since the beginning of 2008 have PCIe slots. The iMac has none at all. Beyond upping the RAM and dropping a different HD into it, all expansion on iMacs (up until recently) has been via USB2 and FW. The latest iMacs sport USB3 and Thunderbolt. FW is gone.
The HDSP 9652 is a lovely card...but PCI only. I had one for years until I bought a new Intel PowerMac....PCIe only.
I replaced it with a MOTU2480/424PCIe combo. And I did that because the RayDat was still on RME's drawing board at the time. I would have happily purchased one of those, had they been available. I love their stuff. However, the MOTU rig turned out to be quite reliable and trouble free. It prompted the UltraLite purchase for my iMac.
So, for the iMac, the only I/O recourse is something that utilizes USB, FW (older units) and Thunderbolt. There are scant few TBolt interfaces on the market but tons of USB and FW devices.