u might have to get a 12w7 looks like from what im reading the 13w7 is dual 1.5ohms and the orion2500d is only 1 ohm stable the 12w7 is 3 ohms u could get 2 12w7 that match your amp perfectly
you can use the orion 2500 with the 13w7. just wire it to 3 ohms. that amp does 1200wmrs at 4 ohms so at 3ohms it will do a little better. which i think it would be perfect. i don't know exactly how much you will get with a 3ohm load but its more than 1200wmrs. it would work out very nicely.
power HX2s are nice subs...personally id rather have them than the W7. but if you want SQ i would do what jexx said just get 2 W6s. 2 IDmaxs would work perfect also...idk what kinds of deals your getting.