hi nathan
your c8 will do you for quite a while me thinks
if kyou want to do planets most use webcams like the toucam, but there are much better webcams avaliable. a barlow in there will increase your image scale.
for wider file astro pics a slr is better. most here recomend canons as most programs seem to work for canon cameras, but nikon make fine cameras too, i have just purchased a nikon d40 myself... but not specifacally for astro pics. you will probably want to get a focal reducer for the c8 for when you hook up your slr.