No, you won't. You will have a super loud micced amp tone, it'll have the benefits that come from volume but if you are picky it will not be the same.
I see what you say and... yes trust me: I'm picky!
In my room I have also a wanderfull HIWATT SA212 50watt Custom Combo with 2x12 purple-back Fane... so... i know what an "amp in the room" is.
So let me be a little more specific.
I said "BIG&FAT" and then i said "loud enough". Those are 2 things.
BIG&FAT coz "size matters".
A 4x12 or 2x12 and even 1x12 guitar cabs are big air movers inside the cabs and outside the cabs in the room.
So you need BIG&FAT frfr speakers that can move the same mass of air in your room.
Not just loudness ... but air moving.
I agree with you: the cab IRs are "micced cab tones"
But there are many micing techniques: close, not so close, ambient, front, rear... and even inside the cab.
Like many ppl here i have tons of cabs packs and while some sounds like "that cab on that record", others sounds more like "that cab in your room". Some IRs sounds only "frontal" like a poster on the wall and some sounds more deep.
When we talk about a good tone we use words like "3d sound" or "360° sound" or "amp in the room"
But we are all refer to one thing: reverb. Better: micro-ambient reverb and macro-ambient reverb.
The micro-ambient reverb is inside the cab. The macro-ambient reverb is in the room.
A good IRs mix that use close micing of the cone and a little bit of rear micing of the cab can get you a good representation of the micro-ambient reverb of the cab. So you need this FIRST.
When you say "amp in the room" you think to the cab sound. WRONG!
Coz what you are talking about is: YOUR ROOM sound!
So, after the micro-ambient reverb of the cab IR (mix), you need a reverb (fx block) tweaked like the natural verb of your room (pre-delay, early reflections, low and hi freqs, ducking time and cut-off etc...)... AND.... even a micro-delay fx can help you to get YOUR ROOM ambient.
I don't want boring you with my crap english, so that said i want take another way.
What appens to your wanderfull "amp in the room" tone with your real cabs if you put a stereo reverb pedal fx and maybe even a delay in your chain?
The "amp in the room" feel is gone? YES!
Ok... that's what i'm talking about!