well, here is what i found:
yahoo does indeed require a premium svc in order to forward their email; the basic yahoo svc allows you to receive POP mail into your yahoo account.
of course, the reason i am phasing out my yahoo acct is because it sucks. it's better than it used to be, but i still dont like the interface very much.
i found this site: http://yosucker.sourceforge.net/#whatiz
yosucker allows you to forward your yahoo email to other accounts. unfortunately it's programmed thru the macos terminal, which i dont have a ton of experience in. but i've got it pretty close, i think, after a day of fiddling with it. not sure if it will ultimately work, but it's worth a shot.
right now i've got my 2 POP accts going to my gmail account, because i like that interface as far as webmail. it's definitely better than squirrelmail. my mail.app still holds all my emails on my home computer, so i have quick access to those as well.
i guess i'd love to be able to send emails from one acct while having them filtered thru another acct so as not to confuse people when i reply to them using a different email than the one they used to send me the original message.
thanks for your suggestions!