[trsqr]

Can I use the same remote for my tv too?

Most likely not. If you want to use the same remote for all your devices, you'll likely need something like universal remote control (Sony RM-VLZ620 is what I've got, Logitech Harmony seems to be popular as well).

You can also go for 1x4. And buy another 4gb later if you want. 4gb should be more than enough.

2 similar modules does activate dual channel mode though, which is a bit faster. Probably not noticeable in media center use in any way though. I've got currently a single 2Gb module and that seems to be well enough for OpenELEC. I've got another one coming though.

Then, is it better a D34010WYK than a D54250WYK for this purpose? Play all kind of contents with a very fast XBMC menus. I don't have im mind to run windows neither videogames.

I don't think the D34010WYK is better for anything else than your wallet. That being said, that's what I got and find that it can do anything in OpenELEC that I've thrown on it (with very fast menus).