Is there a better way????

hi all...I have sony bt 5000 head unit which is feeding front & rear speakers (4) directly via iso
aux connector on a puegeot,so far so good, also connected to the head unit via its FRONT
pre out rca sockets Is a Maystar QXT 200 2CH AMP is feeding a 10" sub 450w every thing is working but my question is this.........Is there a better way to connect up????
I feel i should have gone down the "4 ch amp route" which is still possible as i can get a
a mutant 480 4ch amp for £90 new and have it by 10am today....cheeper online you may say....wont get it till tuesday at the earliest i would say.......is it a good amp? do i even need another amp?...........all suggestions will be greatfully recieved thanks in advance

added later....

I may also have a chance of a maystar mx455 4ch (the one i shoul`ve got at first)....which would be the better amp maystar or mutant??
in the sony h/u install sheet it shows head unit connected to 2x amp units (one for rears the other for the fronts) via 2 pre out chnnels + front & rear also connected directly to h/u, not to mention the sub connected to the h/u sub pre outs.....is this setup possible or am i ,well you know,
"""anyway my head is a raging torrent""""
again many thanks