I originally said (and actually repeated in the post you quoted), that his system is fairly close to balanced already.
As far as how games tax the CPU and GPU, the pace of 3+ thread games will likely pick up in the future, but unless the majority of games he plays use 3+ threads (i highly doubt it), he's better off with a GPU upgrade first.
The individual cores on a 2130 are the same as those in a 2k series I5. There will be little difference between an i3 and a similarly-clocked I5 in 1-2 thread titles.
Don't get me wrong, if he were building from scratch, I would recommend a quad core (or more) part, but as his system is right now, the 7770 is the (slightly) weaker component for most titles.