4 volt to 2 volt to 4 volt

Hey all, I'm new to this site and really like what I've seen of it. I've tried a search of this topic and was unable to find the relevant information I seek. Just a brief intro: I started installing stereos when I was 12 , but apparently I'm old school now, lol. I must be when I find amps online labeled "old school" and they're about five years newer than the last amp I sold when I was in retail about 13 years ago. I was selling mainly Alpine and Phoenix Gold. Anyway, I'm beginning to resurrect my interest in car audio and security due to the fact that my son is about to get his license a just bought his first car. I'm in the process of putting together a system for him using what I remember from back in the day. I'll age myself by telling you what my last system consisted of: Alpine 7618/5950, 3401 parametric, 3656 6-way active, two 3554's, 3522, 3544 running a pair of each of 6660, 6011, 6022, 6180, clarion 4", (1)6015. All I have left is the deck, changer, 6022's, 3401 & 3656. I'm planning a system for my '87 Grand National trying to use equipment from that era so I've got a start. But the main reason of my post is because of my son's system in progress. I'm looking at getting him an Alpine 9887 deck and know that they have 4-volt pre outs. I have already purchased an mrv-f400s, mrv-f300 and mrv-t1000 and am fairly certain they like 4-volt ins. From my understanding the Alpine ere-g180 11-band is 4-volt in/out as well. Finally to my original question: How well would it work to run older(likely 2-volt in/out) Alpine 3658 active x-overs between the eq and the amps to seperate the mids and tweets? I've never been really big on using the built in x-overs on the amps, passives or  y-adapters on the RCA's to the four channel amps. So the two-way actives would really fit my need here--if I can use them without incident. Or do I buy a 2-volt HU & EQ and up the gains on the amps? I appreciate any feedback on this situation, thanks.

P.S. I have also recently purchased a lot of Alpine security systems like I used to install(8040, 8027, 8030A, 8051, 8047, 8045, etc.) and some of them have come with wiring/install literature. Some of which you do not already have listed in your downloads page. I'd be happy to share what I've acquired with anyone interested.