You should be able to get around $300 for them, the Series 1 is pretty old now and you can buy series 3 for about 6-800, so you won't get $600 for a Series 1. The other issue is their size and weight, shipping them will cost a good $200 give or take. So your best bet is a local sale, use a local buy-sell website.
And yes, although Bose is not considered high-end, that's not what the OP is asking for help on. Hope this helps.