Don't have it in front of me now, but I'm pretty sure the Honda manual has a spec on fork spring overall length, so you could measure your stock ones and see where they are relative to new. For lighter riders the stock springs will work, you may want to preload them a bit more than stock (install longer spacers using 1" PVC pipe) and use heavier oil (as you are with the 10w oil you bought). Heavier riders or two up tend to go with stiffer springs because you can only do so much with the stock spring rate. If you fall into the lighter rider category (I'm 170lbs and use the stock springs) I'd try adjusting preload first because its basically free so you have nothing to lose.
re: buying replacement OEM springs, I doubt yours are sacked out enough that putting the same spring back in would make any noticeable difference, but I'll get back to you with that measurement and you can compare