new components for existing setup choose

So this is my first time here. I have been doing my installs of the entire car system on my own for past three years by reading online articles and watching youtube. Have already gone through three changes and every time I have managed to achieve better and better sound. Now I wish to upgrade my rear speakers. I am thinking of sending the front rainbows to the back trunk and face the driver direction?? Does that cause some issues with sound? Rear doors don't have speakers so not sure if I can cut and install. What are the amazing speakers that you may recommend?? My Choices as of now: by browsing online- 1) Focal ES165KX2 120watt@2ohm ES 165 KX2 - Focal (Price: - 570 euro) 2) Gladen ZERO PRO 165.2 PP (Price:- 679 euro) very expensive GLADEN GERMAN TECHNOLOGY Compo Coax Loudspeaker 3) Hertz MLK 1650.3 LEGEND (Price :- 689 euro) very expensive MLK 1650.3 - Hertz Mille Legend car audio speakers system 4) Rainbow Germaniums GL C6.2 (Price:- 429 euro) Germanium Line - Rainbow Car Audio very similar to the SL Pro's that I Have. Please recommend more. Not more expensive than these but can be under. I will order in europe and have a friend bring them in. Thank you so much and please give any advice you may have, I know nothing and thats my attitude so I can learn more. What I have as of now... HU : Alpine - W265EBT with inbuilt crossover that I use. Front Speakers:- Rainbow Sound Line Pro SLC 6.2 PRO 120watt@2ohm which I have set to 63 hz with a slope of 12. Had set it to 50 hz earlier but I think I damaged one woofer a bit. it does mild farting sound at high volume... not sure. but at 63hz@12 slope its good at full volume and mild gain. ( the link to the speakers:- Sound Line PRO - Rainbow Car Audio) Rear speakers:- 6x9 Rockford Fosgate (4way- Cheap tweeters and very sharp but the bouncing from the roof actually compensates.) 75watt@4ohm in the open trunk of my suv firing upwards. They are in a box each. Amplifier:- Rainbow Germanium Four 105watts@4ohm or 140watts@2ohm. (four channel) Is it important for my components them to be under 105watts@4ohm? or 140 watts@2ohm? Subwoofer : 12" Rockford Fosgate Punch 250watt@4 ohm. Vented box by rockford. Amplifier for subwoofer: p300 mono class A/B tiny amp but powers the sub decently. set at 100 hz with 1/4 way punch eq(slope?) not sure about that. Wiring: 12 AWG pure copper (C&E) OFC RCA : rockford Fosgate Have a 2 farad capacitor but everyone seems to think this is a waste and I should chuck it. views? Amp is on a 4 guage main with 8 guage from a splitter to both amps. The doors are deadened and the wooden rings installed for the components.

My personal recommendation? Dump the rear speakers altogether, and spend that money on a GOOD DSP/crossover (a la Audison BitOne or BitOne HD (although the HD version would be WAY overkill)) for the fronts and bi-amp/bi-wire those. Remove the passive crossover. You'll achieve better soundstaging, and probably be even happier with a bi-amped/time-aligned system up front, as you'll be able to match everything, all the way around, and from my experience it disposes of any nasties that your passive crossovers might be adding. SQ competition caliber sound systems do not generally have rear stages. If the cap is there, leave it. My experience is they don't generally HURT anything, but to add one to fix anything is a waste, since they fix very little, IN PRACTICE. My $.02US.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."