Have you ever duplicated another system that you heard?

I have and it sounds glorious.  Would you do it? 
Yes. I always tell people that ask me for advice, to go out and find a system that they would like enough to buy. Building a system in your head never sounds the same as the one you build in your listening room.

True. My build turned out great for me. Just depends on a number of factors.

I, too, am in this process. Happy Listening!

I saw and heard my present high-end "A" system first at a dealer.... it impressed me enough to re-audition it several times over the following 2-months.

I eventually traded in my current "A" system gear at that time, and I cheerfully bought the same system components in the dealer demo system.

I did mine from the components all the way down to the power conditioner and cabling.  I had actually loaned the guy me source and the rest was his system and it sounded glorious. So I took my source and just finished the re- creation.  
First and only time was a Magnepan Tympani 1a system, with ARC electronics and a Technics TT. Bought the speakers and then gradually upgraded the rest to ARC. Glorious.

Learned enough from that system to upgrade piece by piece, and now DIY piece by piece. What a journey!
Doing it as I type.  So far, so good! 
My situation was unique.  Me and 2 of my audiophile buddies spent 5 years trying to outdo each other. Then we started helping each other. One of them took a huge risk on a Gato FM6 out of Denmark. At first we were like crazy! No way! Then they broke in. Then one of us heard about the KR audio va900 then one of us bought the Resonessence Mirus Dac and Clarity Cable and mavros and then wammo! Sweet music.  Unfortunately our craziest audiophile buddy out of the 3 died 5 months ago but he left me with a system that I will enjoy for a long time. God Bless Charles Threatt. Charles and my friend Bill Smith took me on a journey I finally finished happy. Enjoy your systems while your still breathing everyone. They are a sheer joy to all of us!