Upgrade 001 to Mix or HD?

[WannabeSQ]

I am currently using an 001 for post, until we get a HD system, but the 001 will still be in use, and having already hit the wall of limitations, I am considering upgrading to a TDM system. HD is nice, but I don't think its necessary, considering we will have a HD3 for our main mix room, this will be the secondary room, with an 002R for foley and ADR. I know that mix systems will no longer see software updates (as with the 001) but is that really a dealbreaker? I don't need high sampling rates, etc, just more than 32 voices, and surround panning. the CPU is a dual 1.4ghz G4 and rarely is it taxed beyond its capabilities, so either a Mix or a HD1 would work.

Should I bite the bullet and save for HD? Or find a cheaper Mix rig on ebay? Im thinking the HD is a must, but im just fishing for alternatives.