My 2 cents, from a guy who have several 550s and BB s and in the middle of converting a bb1 to a bb2 is to keep your 550 as is. And buy a BB1 reel machine and convert from there. Should be your cheapest option. The BB2 cabinets are amazing but way too expensive. As far as the bb1 cabinet, which ever way you go(video or reels) its best to get the proper topbox size if you want it to look as close to original as possible with the upper screen being displayed. I have dual screen topboxs on my machines and the upper 22" widescreen isnt as tall so theres a void to fill.
The guys commening on this post can correct me on the size top box to best fit the screen, but i think its around 15".