Best Approach to Recovering to New Hard Drive

I have Acronis True Image Home 2012 which I purchased just prior to receiving my (then) new laptop. The hard drive has two partitions: the C: primary and a Q: recovery. I first installed all of the necessary software, but no data. I then created two separate backups – one of just my C: partition and one of just my Q: partition. (I probably should have created a single disk backup, but was/am new to Acronis.)

Nearly 2 ½ years later, my computer is running slowly. In the past, this is the point where I would have reformatted my hard drive and performed a full reinstallation of the OS, my programs, and my data (a formidable task). However, I do have the two tib files which I am hoping will make the task much easier. However, I have never performed this procedure.

Being conservative, I have decided to purchase a new hard drive rather than wiping out my slow, albeit working, hard drive. I want to know what would be the best manner in which to proceed.

I currently have a Seagate SATA II 500 GB laptop hard drive. I plan to purchase a Western Digital Black SATA III drive. I do not need a larger drive, but am wondering (my first question) if it would be better to buy a 500 GB hard drive or a 750 GB hard drive. I question what would happen if the new Western Digital is, in actuality, even slightly smaller than the current Seagate. Please advise.

My primary question is how I should go about getting my original C: partition image onto the new hard drive. Should I attempt to clone my current drive and then recover the C: partition? Or, is it better to recover (from the tib files) all the necessary data to the new bare drive? Either way, I would appreciate some input. I have read the Acronis user guide as well as numerous posts, but am still not clear as to the best approach. Please keep in mind, I am a newbie.

Thank you.

Todd