Geared for the PC: good luck.
I will however say mod your existing kit:
5:1 speakers are nothing special as far as electronics go, the only reason for the central "hub" is to have a unified control point (you can use multiple normal speakers to make ?.1 setup). The controls and the like are probably more than adequate for most people but it is the actual speaker where things come undone for audio quality.
Even though the little speakers are small they are probably quite powerful in terms of wattage (not that it is hard to scale up or down) and you can probably source some good speakers of equivalent wattage (old stereos are a great place to look). There is usually a dedicated speaker shop in even decent sized town/city I have been in lately.