Side + Rear Surround Leads = 1 Lead???

Hi, I've currently got a Creative 7.1 T7900 Speaker system with no digital optical connection through it. I also have the blue box from the Tritton AX360 Headphone package. I'm able to plug the centre/sub, front and rear into the blue box for 4.1 surround (one of the two rear speakers won't work for some reason, though it works on the PC). I can, and have, plugged the centre/sub, front and side leads into the blue box for 5.1 surround but I would just like to know, because the blue box only has ports for front, surround and centre, if I can get a converter in which the side and back speaker leads would go into to form one jack which would then go into the blue box to allow for 7.1.

TIA

It's an onboard soundcard and my motherboard is (description from Ebuyer): M2n-sli Deluxe Atx Socket Am2 Nvidia Nforce 570 Sli Mcp 8gb Ddr2 Sata2 Dual Gigabit Lan Audio. I'm not sure if it's capable of decoding those soundtracks. I'd more like to know if there's a splitter jack that I could put into the middle port of the above image, containing both the read and side surround leads; right now I can only put in the side surround lead for 5.1 and if I put in the rear lead I only get 4 speakers and sub working. I would like a splitter/converter so I could put both leads into one port for sound to come out of all speakers. TIA.iSpray

Kinda skipped this post. But Tritton's blue box doesn't carrry the rear surround through its surround out so you couldn't pull true 7.1 sound from it. Plus, onboard audio does sound weak and tritton's blue box doesnt seem to put out 5.1 channels through its output as in it sounds weak and low compared to plugged straight into the sound card. I'd recommend getting an actual sound card such as this one. *I only link this card because I am currently using this card (except its the fatality edition) and and can't speak for any others. I have my Tritton AX360 plugged in through the front/center/rear channels and optical out to my reciever for my 5.1 system because I can't stand that damn beeping noise these headphones generate through optical hookups. Oh and this sound card sounds #%^ing amazing.*

And I just pulled this from creative's website. "Creative's CMSS tech allows up-mixing to 7.1 from 5.1/6.1 sources." So I think this means your speaker system should have that up-mixing built in and should be doing it when only connected to Tritton's blue box...of course im not 100% on this but maybe an option on the remote it comes with or something allows this? Someone care to correct me if I'm wrong?