The size of the cache does affect the performance of a hard disk - larger caches tend to speed up certain types of operations. A lot of uses of hard disks are sequential access - that is, the next chunk of info you want is just the next portion of the same file you just used. So a hard disk, given a request for data from a file, will actually copy a big bunch of that file into its cache, hoping that your next request will be ready in the cache and can be given to you very quickly. But if you're leaping all over the disk with random access requests the cache helps very little. For heavy random-access use, disk speed in rpm is more important because it shortens the delay in finding the target data.
A 32 MB cache is better than 16 MB because it can copy more data at once and use it to fulfill more sequential requests before having to copy from the actual disk again. In practice, however, the performance of those two cache systems does not differ a lot - just enough that very heavy disk users like server systems may find it important.
Contrast Ratio in Monitors is the ratio of the brightness of a white area vs a black area. Black is never totally without light, and white is never completely white. A larger Contrast Ratio simply means the range of brightest to darkest areas is larger, and makes some things easier to see.
The ASCR thing appears to be ASUS' own version of some measure of Contrast Ratio, and I'd tend to ignore it. Rockford has a point - sometimes comparing spec's is best done within one manufacturer's product line only. If ASUS and Sony and Dell don't all agree exactly on how to measure Contrast Ratio, you can't compare their numerical specs.
ASCR is probably dynamic contrast ratio, while 1000:1 is static. Static matters far more, and is the spec you should care about. Note that any monitor advertising higher than about 1500:1 is advertising the dynamic only to falsely boost their numbers.