What amp and headunit?
What budget for the front doors? rear doors? Otherwise all recommendations are BS.
DSP's are <$300 with a few in the <$200 range. Marts has one on
amazon for $160. And the NVS EQ is on sale for $99 on
amazon, which looks like a clone to the Stetson EQ.
There is nothing complicated with a dsp or eq, and 3 way that sounds well, when compared to pathetic sounding non-eq'd 2-way's that make you cringe.
IMHO, without midranges, you'll have a hole in your front sound stage. You'll expect the door to produce that and it'll be beaming or blocked by your leg. Most tweeters don't play low enough, and is why many Toyota use the 2.75-3.5" dash speakers. For $230,
Amazon/
ebay have the Kenwood xp6903c. If you're budget is higher, infinity/JBL have component 2-way 6x9's available and once you get sick of the loss of good midrange, you can flip the switch and add their midrange. Kicker makes a 3-way 6x9 setup too.
For rear fill, NVX has their xsp65kit for $140 and
ebay has the kenwood XR1800p for $200. I don't care for coaxials since they always sound pathetic when compared to their equivalent sibling component equivalent. But, cheaper 6.5-7" coaxials can be had for the rear door for simplicity and budget, like vtek62, gto629, nvx vsp or xsp, or meso 6.5 for $100.
Just power the passive crossovers by your 4 door(and dash)channels. And, if you add a sub, you can cut the bass out of those 4 channels as most tolerable amps have a crossover. No point in overly stressing door midwoofers if/when you get a sub running. Without eq or dsp, you're limited to whatever you headunit offers for bassmidrangetreble tuning, which might be enough.
If you want to spend a little more research time, you can do well with the speaker choices from CDTaudio, which usually has monthly sales. They have excellent 6.5-7" and 6x9 speakers for your doors. They have widebanders and coaxials for the dash too.