This is a well covered topic on AAM, you can do a search and see various discussions.
My quick summary is a local agent vs the Big ones (Sherryfitz, Gunne). By all means haggle like a bugger as it is easy money for them. Pitch one against the other. The amount of movement of the market in your area will help decide if you need a huge network , sherryfitz, or if a few ads in the local rag will help.
You can do a lot yourself to help, having the ready for sale, Andrew Winter does this to death on Channel 4, if you have it (aren't you based in Switzerland, if memory serves?). Or try and sell it yourself, there are a few sites out there which help, you can get sign printed up fairly cheaply and save a packet, but this depends on the demand in your area. This would be my preferred option if I was do it again, it can do not harm and is fairly cheap