I agree with Inna... you should seriously consider used speakers. Then if you are not satisfied or want to try another flavor you can move up, lateral or down with little financial loss.
BTW, as a previous Dynaudio C4 & Mac MC275 owner, I can tell you that the MC275 will not have enough muscle to drive the C4's, but your Mac 501's should work nicely. Keep in mind the C4's need room to breath (at least 350SQF), need to be pulled away from all surrounding walls by at least 48" and are not very good @ low to mid volume levels.... they need to be cranked up to sound their best.
BTW, as a previous Dynaudio C4 & Mac MC275 owner, I can tell you that the MC275 will not have enough muscle to drive the C4's, but your Mac 501's should work nicely. Keep in mind the C4's need room to breath (at least 350SQF), need to be pulled away from all surrounding walls by at least 48" and are not very good @ low to mid volume levels.... they need to be cranked up to sound their best.