I did a little price comparison of power batteries and stumbled upon this: http://www.akkukauppa.com/nokia-5800...-2800-mah.html
Since N900 and 5800 uses the same battery, i thought of buying that one instead of Mugen 2400mAh battery witch costs 95$ (69€)
With doing so i get 400mAh extra for half the price but i have to order mugen battery cover or make a little something from my spare back cover.