If you've ever had to record a guitar lead over some MIDI tracks using an SB16 - you definitely understand the term latency.
IMHO - there's a lot to be said for some of the higher end sound cards, soft synths, DXi, Recycle, samples and other computer based music products on the market. However.... one has to evaluate ones needs and follow the 80/20 rule.. you can get 80% of the results for 20% of the cost !!!
And I don't recall if it was Tekminus or Equlaizer that said it, but 99.99998% of the time I have taken something I have done [studio or live] and asked for a sound quality opinion from someone other than a sound engineer or other audiophile - they simply can't tell the difference between average, good or great !! They are conditioned to look for the hook. Other than something mastered to cassette tape using a cheap portable, battery operated device, they simply can't tell.....
Instrument definition, separation, phasing, effects and so on, generaly get lost on the average listener....
My point being that if you are happy with it and your sound guy/mentor is happy with it - there's little point in trying for that extra 20%....... no one other than you will be able to tell the difference !!

That's not to say one shouldn't strive for perfection, but at some point - be that based on budget, temperament or boredom - enuf is enuf.
Marketing folks make a living out of making hte perfect demo and making you go out and but that upgrade. It works.. just ask Microsoft !!!

Regards,
Steve