If you want 2 monitors, go with a 20/20, if it mates with your new planter well.  If you are only going to seed monitor with your integra, get a seed only monitor.  That's what I do.  Then you can keep your 750.  If you want all in one go with the fmx.  I got my first fmx this winter and now I wish I could afford to upgrade all the 750's.  I don't have any trouble with them, but my help is all over 65 and the fmx would help them.