If background noise is your problem, these will def do a great job for you. Etymotics triple flange inserts have like a 92% noise isolation rating, among the best. The $170 is pricey, I agree, maybe wait alittle while. I heard that soon double driver sets are comming into the $170+ range, might drop down all the single driver options quite a bit.
I didn't really waat to pay $170 myself but just got tired of using my apple buds. And when I really thought about it, waiting for the set to hit $130-150 its only saving you like $40 bucks. Thats like the price of a nice shirt/pair of pants know what I mean. Just depends on if you wait to save the extra money or not. But spending $130 or $170 pretty much feels the same, lol.
Either way, goodluck on what you decide to do.

Btw that HF2 set won ilounges best of show '08.
And FYI you can't compare the CX300's to the HF2's, thats laughable. The CX300 does offer good balance but it doesnt really compete with any models from Ety, not even the 6/6i. I would however take the CX300 over Skullcandy/VModa and such.
The only sets really that would offer a significant sound difference would be the Shure SE310s-530, but then your talking $300-$500+, those monitors are really in a class of their own. For $170 you cant really beat the hf2's currently.