The Creative cards ain't bad hardware. The drivers suck and there is loads of bloatware. Otherwise, I managed to mix fine on mine 12 years ago or so. and as pointed out above, latency isn't a problem as long as you are mixing.
One thing, of course, is that even if another unit is slightly better, if you have the skills and an engineer's ears you should be able to make use of that slight improvement. Just like a better instrument, or room or anything else.
I don't know if it is still a problem but my old Audigy worked at 48 kHz. It did recalculations for any other spec - on the fly. And that was badly done. something to be aware of.
I still think the best deal around is the Tascam u-7000 for $400. It provides 2 premium preamps, great conversion (it has been called a poor man's Lynx's Hilo but I wouldn't go that far), USB and digital in/out. You could integrate it into your Delta recordings if it has digital ins and can use USB for your mixing.
good luck,
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