Hi Cornwall IVs vs RF7-III,
Since you've been asking, I might as well put in my two cents re the two speaker designs. I believe you said you currently own both the newer Tower type and the Cornwall IV, so why not keep both? I have both styles and I've assembled two separate systems, one for each speaker type. Variety is the spice of life!
Another thing I'd say is that if your music is electronic dance music, I'd go with the RF7 - except that you're gonna be running a pair of subs with your mains, so in that case, anything goes!
Isn't electronic dance music kinda top-end/low-end like the Drum & Bass genre I've recently fallen in love with? I've listened to D&B with both Heritage and Tower models and I must say that the towers put out that "Oomph!" type of Bass more than the Heritage [to see why, look at the travel distance on the two models' respective woofer cones while they're playing a bass line].
I always switch to my tower system to listen to D&B for this very reason [plus, I'm driving my towers with a powerful vintage Japan-made Marantz beast I bought used, and you want lots of solid state grip to properly project loud, powerful bass [hint: don't sell your big Emotiva amplifier!]
[Another hint: look at the power-handling specs of RF7 vs Cornwall]
And since you have both Heritage and Tower, you should look at eventually buying a used tube amp as Shakey advised and pair it with the Cornwalls. The Cornwalls are more revealing of their upstream components, so you'll get a more rewarding sound change with a Heritage/tube/class "A" combination than with the Tower [use your Emotiva for Towers] and besides, the Heritage stuff was specifically designed for use with tubes.
If you get into music that has a lot of vocals and acoustic instruments, the Cornwalls will DEFINITELY prove superior to your Towers. Don't get me wrong, the towers sound good with vocal/acoustic, but aren't in the same league with the Heritages when it comes to tonality - especially mid/upper bass and mid-range tonality - which is a big reason they're still so popular [along with higher sensitivity and better dynamics].
Speaking of Heritage advantages, if you're going to do a lot of low volume listening to electronic, or any other genre, for that matter, then DEFINITELY use the Heritages for this. I don't think there's ever been a speaker made that can compete with Klipsch Heritage at the lower/moderate volume levels.
Lastly, if I misread your post and you DON'T currently own both, I'd highly advise you to go online and score a pair of used Heresies. You mentioned money constraints and I feel your pain because I'm in the same boat [I'm not wealthy], so I can assure you there are super deals on mint-condition Heresies out there. The Heresies alone are awesome-sounding, but teamed up with your two subs, even the [relatively] little Heresies [not to mention Cornwalls!] will provide unbeatable sound. I'd put a pair of sub-matched Heresies/Cornwalls up against ANY OTHER SPEAKER AT *ANY* PRICE.
But without subs, I'd always favor the Towers for loud, bass-heavy music and for most all other music styles I go strongly for Heritage.
But the main thing is to own both types. I'll never regret doing that, esp since I bought used, therefore I got two clean, unscratched systems for the price of one.
Hope this helps!