Reddit mentions of 6.5 Inch (6½") Black Plastic Speaker Adapter Bracket Ring Select Models Fitted For Nissan / Infiniti

For the door speakers, you need a set of brackets. http://www.amazon.com/gp/product/B007ZQVKYM/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1 These worked perfect for me, as for the tweets, the component set I've installed is from "West Coast Customs" (Not overly happy with them, this is stated not as a recommendation, but as a "this works"), but their 1" tweets fit perfect with the stock tweeter bracket, no cutting or anything.

If you have experience installing speakers in your car you could save some dough by doing them yourself but they’re not the easiest to install in the rear deck. You gotta remove a good amount of plastic to get to the two 6x9s and then there are two speakers in the rear seats as well that you need to remove the rear plastic. The front door speakers are easy but you gotta buy spacers for them. As far as brands go, for the head unit this Sony unit is awesome Sony XAVAX1000 6.2" (15.7 cm) Apple CarPlay Media Receiver with Bluetooth https://www.amazon.com/dp/B07JDFKQJ5/ref=cm_sw_r_cp_api_i_ZH9NDbN89V8BH and speakers Pioneer TS-G1620F 600 Watts Max Power 6-1/2" 2-Way G-Series Coaxial Full Range Car Audio Stereo Speakers https://www.amazon.com/dp/B00A0LZHYS/ref=cm_sw_r_cp_api_i_fY9NDbGY26QS0 and rear speakers Pioneer TS-A6965R 6" x 9" 3-Way... https://www.amazon.com/dp/B00A0LXRL8?ref=ppx_pop_mob_ap_share
And you’ll need these spacers Nissan / Infiniti 6.5 Inch Black... https://www.amazon.com/dp/B007ZQVKYM?ref=ppx_pop_mob_ap_share all for under $1000 bucks!