I think the answer depends on whether you'd rather spend several hours grappling with CSS, or several hours grappling with PHP.
My brain architecture is incompatible PHP, so I wouldn't want to mess with that, but I can tell when something looks good and so would do the CSS thing.
I do think that there needs to be PayPal standard built in to the next release of PowerStore. For the monthly cost of PayPal pro, see what you can get for a similar amount here (including PayPal Standard and a choice of 300 design themes) . Of course the downside to that is that you don't own the product, but I don't imagine a client would care too much who he paid the monthly fee to, and the ongoing responsibility wouldn't be yours.
I understand that WA will be adding templates to PowerStore at some point which will add considerable value to the package.
You need to hear from a WA person about your original post and queries.