Sound Storm LaboratoriesEV400.4 Evolution 400 W, 4 Channel, 2 to 8 Ohm Stable Class A/B, Full Range Car Amplifier, Black

Q: can u still connect this amp if u only have one set of rca in the back of head unit ?

Yes you can, it only requires 1 set to operate, I don’t recommend this item though, I ended up sending mine back because it didn’t work properly

Q: just need around 45 more watts to ONLY my highs mainly, but to Mids as well- anyone with this amp think it will do what i want???

I have had this amp for 3 years now. One tripped channels 1/2 into protection mode and never came out. I got my money back and put another one in. Not a problem at all. These are great for the four 6 x 9s I run for mids & hi's. I use a ground loop suppressor though. They will wine without one. Not the best on the market, but at 40 bucks, it's tough to pass that up when the quality of sound is so awesome.

Q: Say i wanted to hook this to four 5x7, would it sound any better than the jvc kd-s79bt radio unit i have? It's only 5 more rms per speaker

I don't know about your jvc radio but I use it to push some tweeters in my 2010 Accord. Along with a box in the trunk, they add the sound I needed with the mixing of the extra bass in the trunk.The box in the trunk is on a different amp.