No problem at all
The tube adaptor allows you to place on any 52mm filter with front threads (all of them have them) therefore you're able to "open up" to the world of pro/good filters. The bundles you saw on ebay are just the tube plus their own filters and you have to wonder: ~32.00+6.00s/h for a kit of a adapter, mini-tripod, CP filter, UV filter, hood, and if I remember right, a MC filter too or maybe it was a ND filter is rediculously cheap considering just a CP filter alone can run you up to 180.00; tube is say 10-15, UV filter is about 15.00, MC is about 25-30, hood is about 15-25.00, mini-tripod is about 10-20.00; you can see that there is an obvious question of whether the quality of that kit is anything decent and my bets are noway near the optical quality of a normal good filter.
Terms of Branding (This is actually pretty accurate in terms of reliabilty, build quality, and price bracket)
Hoya is about equal to Lexus IS350
Tiffen to Infiniti G35
Cokin to a Chevy Impala
B+W Porsche Carerra
Helopian BMW 7-Series
Nikon Mercedes S-Class
Optika Geo Prism
Canon Toyota Matrix
Thought you'd enjoy the car terms