I wouldnt bother getting 2 clowns, maybe get a goby or a blenny as well as the clown. This is unless you just want 2 clowns and a large anenome, but remember alot of anenomes like the atlantics and carpets can grow huge, bubble anenomes and even things like torch corals can be hosted quite happily by clowns, but actually they have been seen to host any number of corals, and even things like powerheads! A couple of shrimps would go in a 10G aswell along with a couple of hermits and snails.
In a 10G could either have an internal small skimmer, or an external hang on one. As said earlier you can make one yourself, either using a coke bottle with some tubing and an airpump/stone, or you can make a simple box design out of acrylic, if you have a search on the internet, you will find links to diy skimmers.
Ben