This one looks good, dimension and review wise...
https://www.parts-express.com/dayton-audio-rs75-4-3-reference-full-range-driver-4-ohm--295-380
Dayton Audio RS75-4 3
The only speakers i can find with < 1.5 depth and 8 ohm
https://www.parts-express.com/quam-30c25z8ot-3-moisture-resistant-speaker-8-ohm--244-3222
This one i like but its 1.77
https://www.parts-express.com/tang-band-w3-881sj-3-cast-frame-neodymium-driver--264-812
I am also in the process of upgrading the 3.5. I have the 9 speaker premium version. I added a JL 10W3v3 sub in enclosure with monoamp. Added KST25 tweeter. This sounds sooo good together. Now for mid-range, I am thinking of replacing 3.5 speakers. But I don't know any 3.5 which don't have...
Upon recommendation of the topic starter, placed JL audio 10W3 Sub and KST25 tweeters. Such a HUGE difference for under 500 dollar investment.
Thinking of trading in my 10W3 for 10W6 or should i go for 12W6...i have the JX500/1d amp though. Also I used a LOC, but since i have a premium car...