With a kit you only rack a 2-3 times. You rack from the primary to the secondary after 5-7 days and do not top up.
You rack off of the gross lees after about 10 days if your SG is 0.996 or less, stabilize, degass and add clearing agents and top up with water or like wines. If it is a Wine Expert kit you can use water if you wish and this is figured for in the concentration. I usually use water for this top off.
After 8 days or so the wine will be clear. You rack it again to polish the wine. This time if you need to top off you should use a like wine but if you racked off of the gross lees good in the last rack, you won't loose much at all. You then leave the wine for about a month to clear crystal clear and then can bottle or leave it as is to bulk age.
The moral of this story is if you do a good job racking you only have to top up once with a kit. If you have to a second time it is normally a minimal amount. Also, when I top with a "like" wine I usually use any red that is close for a red and any white that is close for a white. My WE Sicilian Grillo I topped with some Pinot Grigio. My Nebbiola 'dAlba I topped with a Cab
If you haven't started this kit already, I don't think you are going to be drinking it for Christmas unless it is like a WE Vintners Reserve kit that is a 28 day or so kit. Or you like a really rough wine. The higher end kits take a couple months to make properly. Also, in regards to your primary, year, a 7.5 or so is fine. Mine is a 7.9 and plenty big enough. I wouldn't try a 6.5 as it will push the limits and many kits foam quite a bit during the initial fermentation.
Smurfe