Yes, that'll work fine. Although I've never had to amp the sync line before. I've also used just transistors in the old days without the extra components (still working to this day). Nowadays, the current mod uses a THS7314 amp and circuit like this one http://i.imgur.com/MOvIgmrl.png
I did the sync line once and never did it ever again. Absolutely no need IMO. Also, it's much easier to fit a three line amp than four inside that small console.
Nice! I had no idea about the booster that connects on the expansion port. I'll still give a try with the RGB amp since it is relatively cheap to build.