For the typical user, I'd say no. My HTPC (for blu-ray movies) has used both an Optical S/PDIF digital output as well as a 5.1 analog output from my system to the same Home Theater in a Box (Onkyo HT-S3200 - $300). Personally, I cannot tell the difference. Only when you get into the higher price-ranged home theater system might you really notice a difference.
-Wolf sends