Mobo £70.32 click here
<<Ideally i want to be able to route my sound (headphones etc) and USB ports etc to the front of the PC.>>
**3 x USB connectors support additional 6 USB ports,1 x Front panel audio connector**
Case £19.99 click here
or click here
I think your gx card is XFX 8600GT but it won't be SLI anyway.
<<Any fancy extras such as onboard wifi or external sata slots would be nice, but not a priority.>>
There are some but won't be within your budget.