Well......you really need to 'worry' per se, as I'd just suggest getting after market cooling. Even without heavy overclocking I'd suggest it just to preserve the life of the card.
80C+ is normal for a card during full load, but if you're hitting that, just think how it might be on a hot summer day muchless with overclocking.
Normal idle temps can easily be 65C or higher for some people, depending on areas and things like that. Some peoples cards idle at around 55C or maybe even lower.
my 6800GT AGP would idle at 65-70C and hit 85C during heavy gameplay....I knew a guy on here who's 6600GT was hitting 100C lol.
so 80-85C is fairly normal, but personally I'd want to get better cooling