I think you would need to check e-bay or sites like that for it, new Mac's are REALY expensive, also if you want to upgrade you'll need to pay like 150$ for a legal version of MacOSX.
YeahI must agree on that (I prefer Opera also) also the tons of "panels" you can get for it make it realy usefull, FireFox is an good alternative, especially because it's free and it's compactible with most websites.
(sometimes I experience problems with Opera because the webmasters use IE-only javascripts etc )