Universal Audio UAD-2 DUO
I've been happily using UAD-1 plug-ins for several years, but have resisted making the investment in the UAD-2 hardware. The two cards I had generally filled my needs, although I occasionally ran up against their processing limit. When Universal Audio made the offer I couldn't refuse by ending support for the old cards and offering a nice discount for upgrading, I realized the time had come.
Since installing the new cards ( which was a painless procedure) I haven't reached their limit, though I should mention that I haven't yet purchased any of the UAD-2 plug-ins, which I expect would make greater demands of the hardware.
I consider the UAD hardware a reasonable cost of admission to the UAD software; the processing power is an added bonus. Installation was simple and performance is perfect. I remain a happy UAD user.