Upgrade from my Audio Research LS7 to a remote control model?

You could just add this remote volume control and call it a day.  As @newbee said, a new preamp will likely change the sound for better or worse depending on your taste.  If you like your sound as is I’d play it safe and add a good remote volume control.  Placette is reputed to be very neutral and uses pricey Vishay resistors in its volume control so very likely will not change your sound at all.  Unless you think a new ARC would be a sound upgrade for your tastes, I’d just do the Placette.  Best of luck

http://www.placetteaudio.com/remote_control.htm

Wow!! looking at the remote volume control I cant understand why pay $1300 for this devise. I would rather have a better preamp that has better  soundstage and be more neutral than the LS7 for not much more $$ than the volume control. But what ever floats your boat.

mktracy, not to worry I think. I believe OP has posted a 'wanted' ad for the LS15 and LS16 on USAM for a used unit. Not the SP 16 however which I think might have been a good, if not better, choice as well. Oh well.

FWIW used Placettes pop up frequently for about $500. 

Thanks for the suggestions here.  Yes, I've posted a WTB ad for an LS15 or 16.  I already have a AR PH3 phono preamp so no built in phono stage needed.

@dave43 I had a LS-15 for about 10 years and was very happy with it till I got a LS-25MKI. The PH3/ LS15 was a great combo and I think you will be very happy with. If looking at a LS16 make sure you get a MKI not a MKII, the MKI will have the same sound sig as your LS7 just larger soundstage and fuller sounding all around plus it uses 6922. Good luck and keep enjoying the music.