The Marantz Model 15 Amp

I don't think it will be that much different then the receiver you already have. You don’t need the power of that amp (or your receiver for that mater) with any of the Klipsch heritage line.

If it was me I’d find a nice low powered Tube amp, personally I’m not a fan of SS with Klipsch heritage speakers.

But if you own it, try it, you may get different results . And if you already have the receiver then why do you need an amp that you will also need a preamp for? using the receiver as a preamp is not ideal either as most preamp sections of revivers were not as good as separate preamps.

How fresh is the rebuild? Old solid-state gear will lose its smoothness when the caps dry out. Why bother with old gear, there is very good new stuff out there that will sound better. Rogue and Musical Fidelity come to mind. 

I have a Cary SLI-80 tuber. Sounds great. Just love the older Marantz stuff which keeps my Mancave cooler in the Summer. Cary in the Winter. Maybe I’ll send the 15 through my 2226 preamp? What do you think?

Oh. My preamp is a Bluesound Node. Excellent!

Nice amp.

After the dust settles and you’ve become nice and comfortable with the amp, you may consider upgrading the "captive" power cords with something better. I have a fair amount of handson experience wtih vintage Marantz, and your Heresy IVs will thank you for it.

This can be accomplish by purchasing a pair of complete cords, slipping off the connectors at the amp end, feeding them thru the chassis (might take a slghtly larger opening -- be sure to use a proper grommet!!) and soldering them in place. If you want better sound with an OEM appearance that can be converted back to stock, this is a fairly untechnical approach. If you are okay with modifing the back panel, you might consider, cutting out the sheet metal and installing EIC sockets, then use quality power cabling internally. This will allow you to change your power cables as you feel the need to do so. Whacking the chassis of older gear is always at the owner’s descretion. I can fully understand the sensitivities of you are hesitant to do this.