I had started a reply to this using my NT-150, then I wiped out the whole thing and couldn't find an undo, so here goes again from the Windoze machine. :)
I have worked out a deal on one of the supposedly ISA ones with a missing NIC. I'll have to see what this thing is. Since you've got several, let me know if you end up with too many. (Is there any such thing? My wife thinks so...) ;)
As far as upgrading the processor, you'll need the older BIOS I provided a link to in order to change the multiplier. It's undocumented, but if you set the multiplier to 2x on a K6/2 or above, the K6/2 interprets that as a 6x multiplier, so you can get a K6/2 or K6/3 (regular or plus) running at 400MHz max by setting it to 2x.
Regarding the memory upgrade. As I mentioned previously, I installed Windows 2000 Server on mine awaiting the memory upgrade. To see if the memory was the problem with Citrix, I tried that same 256MB DIMM from one of my other machines. This was the same 256MB DIMM that would let NICOS 2.0.9 boot about halfway, clear the screen and hang, and let NICOS 3.0 and DemoLinux 3.0 boot halfway, clear the screen and continue booting with no video. Oddly enough, Windows 2000 Server booted and ran fine on this 256MB stick... It might even be something related to the older version of the BIOS. I'm still waiting on my 128MB TinyBGA DIMM to upgrade it "permanently" to 128MB. I'd love to go to 512MB if this thing will support such a large DIMM. I've not tried that large of a DIMM on ANY of my machines because I've heard there were problems with a lot of older machines recognizing them.
I did get the 2.0.28 iso, but have not been able to test it since I've modified my NIC beyond its original functionality. I need another stock one to play with. :) I did get the mail, but have been swamped looking for a job. Pay the rent or hack? hmm... ;)
Anyway, I'm certainly interested to see this strange ISA NIC with no Ethernet card since the Ethernet is integrated on the motherboard on the one I have...