Forte IV play nice with SS and Tubes. To me they definitely sound different with different electronics. I run mine mostly with my 300b but about two months ago I picked up the excellent sounding Cyrus i7-XR Integrated Amp for a second system. I didn't quite have everything needed for system 2 so I put the Cyrus in my main room to put it through it's paces. I ended up keeping it in there for three weeks it sounded so good.
I was trying to trace a noise down and pulled my 300b out and set up my Quicksilver 40 watt monos. Again, different sound.... not bad but I really missed the tone and timbre of the 300b. Turned out the noise was cable related but it was good to leave the QS in for a little while.
I agree with Parlophone, you should be able to hear the difference. I think the new Heritage are pretty revealing of what's upstream. If you swap out amps to no effect sometimes the preamp can be the limiting factor.