Larkooler is practically unheard of in this forum. It is probably because there is a lack of promotion and also because the price has been elevated once it is shipped out of Taiwan to the US market. Its cost was only about US$90 equivalent when I saw it early last year. Now, the new version (black) is listed at close to US$200 at FrozenCPU. This just cannot compete with the XSPC Rasa kit. Larkooler must keep its high CP ratio in order to compete in overseas market.
Anyway, you will see it receiving fairly good comments in Taiwan/HK forums, regarding its thermal performance and CP ratio. BA2241 will not beat a custom loop but it is definitely better than any single 120 rad AIO like H50/60/70 and I would suggest paying $20 more to get it.
Keeping a CPU-only loop is a good decision as you plan to heavily overclock the i7 920 D0. According to the reviews and user reports that I have read, the kit can handle a 4GHz i7 920 with no problem. For 4.2GHz, adding 2 more fans to do push-pull should suffice. For 4.4GHz, this is going to be a big big challenge and I am not optimistic.
Regarding prices, they are so elevated in NZ! An H70 costs $196? If this is US dollars, then it is ridiculous. If it is NZ dollars (= US$155), then you must consider ordering from, say, FrozenCPU where it costs US$110 + $48 USPS Priority Mail International = $158.