Amps that are "forward"

Interesting question.

Are some amps inherently always forward and others not?

Could be.

I've always attributed that aspect of the sound more to the speakers and room acoustics, but I think I have heard some differences here switching just amps and nothing else.

Tonal balance of the amp may have something to do with it.

The Electron Kinetic Eagle amps have an immediacy that produces music (especially vocals) like you are describing.
They also have killer bass. I'm kind of drawn to this kind of sound too.

If you want to hear more detail I would add room treatment; "bright" sounding amps appear to give more detail but just alter the balance of what you were already hearing. Getting rid of cancellation due to reflected sound will give you more real details.

I believe Audio Research amps (and pre-amps) are a bit forward, all the ARC amps I have had were, a vocalist is usualy a bit in front of the "plane" of the speakers, towards you. I have gotten used to the sound that way and prefer it.
Len W

Adcom GFA 555 and GFA 555II.
The most "forward" sounding amps I've owned.