I'm a Canon guy- so I'm pretty biased and honestly I don't know very much about Nikon. But- google tells me that the D3000 is only capable of running at ISO 1600 & that it's known for getting seriously noisy anywhere past 600.
Again, I don't know what all Nikon's got on offer right now and I'd understand your wanting to keep with your platform so as to not have to bother buying new lenses.... but I can say that something like a Canon T1i (the T2 is just sort of a ripoff imo) has a WAY more competent sensor that'll push out to ISO6400 which will give you far better results in low light. Hell, even an XSi's sensor would probably outpace that D3000. but that's just my $0.02