If you are considering going HD, I would install your 3 receivers yourself first. Then if you buy an HD receiver and call Bell, they will carry out a full Upgrade suitable for ALL of your receivers, so you would get an SW44, extra LNBF etc all for free.....
Providing you did NOT add a second LNBF and subscribe to ANY channels from 82 degrees with your own 3 receivers before you got the HD box.