I wouldn't buy either controller new. The used market is a lot more affordable with C24's going in the $4500-5500 range and S3's around $3250. Also, the C24 needs a bunch of DB25 cables to use the preamps or the monitoring so factor that into the total cost
S3 with the DOCK(and an iPad) can be done for under $4k used, so maybe hit youtube and watch some videos. C24, has been in production for several years so it might not have much longer regarding support(maybe one of the mods can address this concern)