ctviggen,
Your question has been combed over many-a-time over at Audio Asylum...go to the Cable Asylum and type in 'optical toslink'...you'll get a variety of responses.
Tho Toshiba states that plastic fibre is 'good enough' (and certainly cheaper and more durable), but it seems the cumulative opinion of audiophools on opticals is, go glass. And, if you go glass, go 280 strands (some makers, Audioquest mentioned specifically use 65-70 strand glass).
I found an inexspensive option in a SonicWave all glass, 280 strand toslink (at about $35 or so...tho Buy.com has them coming in in a few weks for a lot less), but I bought mine from a guy on Audiogon selling them for $29.99 + $6.95 shipping.
I only bought it last week, so I'm in the same experiemental stage as you.