Both price and challenge...i got the HU 300 and I've never heard of anyone doing this...so far as the amp, a buddy of mine told me the same thing not sure if it has one built in(doubt it) but I don't mind putting one in if i have to...i have a friend that works in a Honda dealer so I'm going to see how much he can get me the original harness from the 08 SI so i can then make the mods to retro fit my hatchy...if not ill have to customize the whole thing (and YES i understand there's a big diff in the harness..another reason why i asked for help...WHICH I GREATLY APPRECIATE)...i actually don't have too much experience in electronics...but I'm up to the challenge and also have a few friends that can probably assist me. PLUS ALL YOU GUY MY NEW FRIENDS!...pretty sure it doesn't have a built in ant,however, i am aware that i need it,i believe an XM radio ant is applicable for my little project( if not someone lmk)...anyways the more help and info the better and the faster i get this bad boy done...I'm currently working on getting the radio wiring diagrams for both my car and the 08 SI so that i may begin the wiring. I'll post pics but its just the HU right now. ANY MORE HELP OR CONSTRUCTIVE CRITICISM WILL BE APPRECIATED THANKS GUYS