Monster 3250 manual It has both RCA (unbalanced) and XLR (balanced) inputs.
The pioneer sc-lx704 only has RCA pre-outs, so you'd use RCA cables. I'm using 3 of these: Hosa HRR-005. There are more expensive ones but stll snakeoil free ones (Bluejeans, for example) and cheaper ones (Monoprice). I suggest using ones based on coaxial cable, as they have good shielding.