When it comes to your wife, there is no winning, only various states of losing.
the best way for anything wife related is to make it her idea.
I wanted a big screen TV in the bedroom. not gonna happen. but, allow me to explain. our TV stopped working. perfect. typical bad caps, not turning on etc. papa wants a new TV...
gotta broken TV honey, need to buy a new one... thumbs up!
Me: (after unpacking the new TV) now what?
Her: (points) you need to get rid of this broken ass TV
M: okay
H: take it out to the garage and then take it out friday (our garbage day)
M: okay
so i drag it out there and change a few caps in it and it fires back up again...
LATER IN THE WEEK:
Her: it's garbage day tomorrow make sure you get that broken TV out there.
Me: right...yeah...I..uhm...took that TV apart and fixed it.
H: wut?
M: yeah.
H: ...
M: ... (stupid look)
H: ... (stupider look)
*proceed to make stupid faces at each other.* (I won)
Her: so...it works?
Me: yeah I suppose you could say it that way.
H: so why the hell did we buy a new TV?!
M: cause the one we had was broken?
H: well...christ!
M: ...
H: so why again did we buy a new TV?!
M: cause the one we had was broken.
H: yeah i got that...
M: a better question is, what the hell are we going to do with that one now?
H: ... *look of disapproval*
M: upgrade?
H: what are you talking about? why?!
M: because I can. (proceed to place said TV onto my desk as if to hook this ridiculously large "monitor" to my computer...)
H: FORGET IT!
M: what do you suggest then?
and that is how I got a big screen in the bedroom.
TL:DR: I got what I wanted because it was all her idea.