For the ride to WFO5 I tried a pair of the 8.99 cheapies from WalMart. Worked just fine. They have flat seams. Some folks recommend the kind without seams, but it seems that my butt wasn't that sensitive, the cheapies worked fine for me. I'll probably try a different pair for my next LD ride just to see whats available/different. Haven't been to the point where I felt like I needed the 'MonkeyButt' powder, I always just stand on the pegs for a few minutes, seems to work OK...
Good luck on your SS1K. Tunes & earplugs seemed to help keep me from getting too drowsy during my rides last year. If you are a coffee drinker like I am, wean yourself off of coffee a few days before the ride, get a good sleep before you start, and get a coffee at the 800 mile point if you need it. That and some jumping jacks, along with on the bike exercises worked great for me. YMMV etc etc
Post up a ride report when you get done!