If you want to keep budget down look into soundsteam 1000d, CV amps, and I'm sure there are a couple other options at that price point.
Polks don't sound good to me so I can't help with those speaker options.
See if you can listen to some other bikes and find what you like.
2009 Road Glide. 16 in Vindikta Wild Cats. Aquatic AV, Stinger 700X4 to MMatts, Audiopipe horns.
6900pros in the lids w/ sspn.4 1000d, tuned with DD Audio DSI-2. S&S 106, lifters, push rods and AC. Drago 2. CycleRama 575. Progressive monotones -1in. 12in. HD adjustable rear shocks. Painted inner fairing. Tuned with TTS. Blacked out!