[flexoffset]

I don't think you can directly change the buffer settings on the actual audio card interface software. You can do it from your DAW, though.
The way you do it in Logic is this:

Go to prefs -> Audio Hardware & Drivers
There's a drop-down menu that allows you to change buffer sizes. I think maybe Logic ships with a 256 sample setting.
I know my Lynx L2 must have 1024 for now.
I know a person who has the same issue with his Lynx AES16 card.
Anyway, see if lowering the sample buffer size will help. You'll know when you get it too low as you'll get crackling and fizzing in your audio. The lower the buffer setting, the more processor resources you'll require.

When I had my M-Audio Delta 2496 card, there was hardly any latency, but the A/D and D/A conversion was less than optimal.

Soft synths are tough to play real-time with buffer settings this high.