I was wanting to purchase one of the downloads from the site but can’t seem to figure out if they are relevant to my 453.
There are two basic differences between styles for PSR-E models and styles for PSR-S models:
(1) The PSR-E models can play "SFF1" ("Style File Format 1") styles, but not "SFF2" ("Style File Format 2") styles. "SFF2" styles have more parameters and can use "Mega Voices." Fortunately, there are free utility programs which can convert "SFF2" styles into "SFF1" styles, so you can safely buy either type of style. You won't be able to use the "SFF2" styles as-is, but you can easily convert them into "SFF1" styles so that you can use them.
(2) The PSR-E models can play two variations per style ("A" and "B"), but not four ("A," "B," "C," and "D"). Fortunately, "SFF1" styles that have four variations can still be loaded into the PSR-E models-- unless they exceed the size limit (about 50K)-- so you can use their "A" and "B" variations; you just can't use the "C" and "D" variations. However, there are free utility programs which let you remove any unusable variations from files that exceed the size limit; and they also let you rearrange the variations so that you can choose which two variations you want to keep. Thus, you can safely buy styles that contain four variations and then split each one into two separate styles (i.e., variations "A" and "B" in one, and variations "C" and "D" in the other).
Another issue common to all models is that you'll often need to "revoice" a style for your particular keyboard. On the one hand, the original style might use some voices which your keyboard doesn't have. On the other hand, your keyboard might have some voices which sound better than the ones used in the style. There can also be differences as to which effects and other settings are available from one model to the next. For these reasons it's always best to inspect a new style to make sure it uses only voices which your keyboard can actually play-- not to mention the best-available voices-- and make any other tweaks to capitalize on your keyboard's capabilities and to compensate for its limitations. If you know the style was designed for your model, or has already been tweaked by someone else, then you can just use it as-is. And in many cases the style will still play and may sound fine even if it hasn't been optimized for your model-- but if you're serious about your styles (as many members are), then you'll eventually want to roll up your sleeves and start tinkering around with your collection of styles to get them sounding "just right." Again, there are free utilities for that.
So the bottom line is that you should be able to buy any of the style collections. If some of the styles won't play because they're "SFF2" files, you can easily and quickly convert all "SFF2" files into "SFF1" files for an entire folder. Most style files will work just fine after that. Then you can tweak them at your leisure to use your keyboard's best voices or to choose which variations you want to keep.