oh, that's what actually the spirit of head-fi is..you're really bound to spend more than you'd ever think of. But then as always, Good Luck On Your Wallet Dude.
i have read several good reviews regarding the Thinksound Rain and that should be a very good buy for you, and for the nature too. And as for the Sennheiser models, the only one i found to be noteworthy is their CX95 which is renamed to CX550 Style II which should be priced lower anywhere now. I've tried them and I find Soundmagic's pl30 and pl50 to be even better.(YMMV). Try Fischer Audio Eterna, they're very highly rated here, even regarded as a Sonic Diamond (CliesOS's words) alongside Head- Direct RE0 if i remember correctly.
First of all, I mentioned that I would like to buy the thinksound ts01 (thunder) IEMs , not the rain :) Also , do you (and anyone else) think that Seenheiser CX 550 Style II are better (in Sound Quality & in general) than the Brainwavz M2 ?