DGAust is 50% correct, but not entirely.
The IR buds and the MS receiver (the USB thingo) CAN be used to re-transmit ANY IR signal you need to.
However you need to use a 3rd party driver for the MS receiver.
This can be either Girder (
http://www.xpmediacentre.com.au/comm.../www.girder.nl) or HIP (
http://www.byremote.com.au/Hip/).
My preference is HIP as its free....and best bit..no additional parts/soldering required!
Basically, using the modified MS IR driver (included in the full download or find the remote your using), you can program the HIP driver/interface to use (for example) the coloured buttons on the remote to re-transmit (via a blaster) to another device.
It means you can program the HIP driver your Amp vol up/down IR commands to be re-transmit via the MS receiver blasters to your amp, when you press the vol up/down on your remote.
Bit of fiddling I know, and I should point out that previously you lost the 'triple tap' (i.e text entry via the remote) capabilities.
Anyway, should solve your problem. Needs a bit of reading and playing to get it to work, but the download does contain a standard MCE remote layout, so all you would have to do is modify the vol up/down to learn your amps vol up and down, and get HIP to re-transmit via a blaster.
Incidentally, the thing I liked is that you can set the HIP driver to send out specific commands to specific blasters (ports) so amp commands can go out via port 2, and STB via port 1 for example.
Hope it helps.