UM i will disagree with a whole number of things here.... YES it DOES make a huge difference to have on multiple X class (if its on a dif a or b it is by definition on a dif c class) A.B.C.D
UNAGI+++
OP has 1 site, so none of this really matters. However.
I agree that if you have interlinked sites, a blog network, etc, that you don't want them sharing ip space. However, A/B/C/D doesn't really matter, what matters is "distance of netblock ownership".
Take 4 ip's as an example.
9.1.2.3 ( Class A, IBM Owns It)
128.1.2.3 ( Class B, BBN Owns It)
199.1.2.3 ( Class C, Sprint Owns It)
204.1.2.3 ( Class C, NTT Owns It)
If you had 2 blogs, and wanted to put distance between them, does it matter which of the 2 networks above you pick? Nope. Picking the two "Class C's" is just as good as any other choice. Different networks, different owners, different geographic and network locations.
And, I don't want to bother with explaining the deeper example of CIDR versus classes, but it's also possible to find 2 networks you might call "Class C" networks that are very close in number, but far apart in geography and ownership. In fact, my example above is somewhat flawed, as block ownership doesn't have to fall on the old-style A/B/C boundaries.
This is why all the "Class A/B/C" stuff bugs the shit out of me. It's not accurate anymore. CIDR replaced IP classes in 1993.