i'd sell the celine first b/c i think it's a trendy bag that won't withstand the test of time. however, if you love it then definitely keep it! between the cerf and gst, i'd sell the cerf.
Personally I would get rid of the Cerf. Cream is a hard color to keep clean in a tote (especially if you carry them full and they always drag across your jeans) and I prefer the shape of the other bags!
you said you rarely use the cerf or the gst so i would sell both of those.... Since you don't use them.