X-spec... whatever you do.. BRING along your transmitter to the LHS when you purchase your set.
Insist to try the cables and software there. If you check the local forums (DH), you will find a few of us came across cables that didn't worked properly
and had to make several trips to the LHS.. They do have a USB capable PC that can check.. and will usually insist that they don't until you make that 2nd or 3rd trip down.

Reflex do not come with an interface. It comes with a dedicated cable.

You will need to get an additional DSC cable so that you can use the interface.
Do not get the DSC cable from that LHS, the one they sell don't work properly on some PCs and needs manual soldering...
Instead, head 2 levels down to purchase the DSC cable from SHS/NTC.