Wireless Networking → Most power-efficient wireless adapters for a laptop?

I have quite a few working laptops with batteries that hold a charge, most with Intel-based 802.11n solutions (2x 4965agn MM1 full-height, 5100agn half-mini in another, etc.) and these seem to take up considerably less power than any other chipset I've tried for 802.11n communications in those laptops, on battery power. I'm hoping this will also be the case soon as 802.11ac devices mature, but that's a long ways away, yet.

My current issue is a laptop that I bought back in September 2012. it's a Gateway ML3706, which uses a motherboard shared across about 26 different other models with the same chassis, as far as I can tell. The wireless adapter initially sent off with this laptop was a junker Realtek 8187 chipset that doesn't seem to play nicely with 32-bit Windows 7. The BIOS isn't whitelisted, so I can install any wireless adapter I want without worry... but this is where my big issue with this laptop starts.

The laptop has a MiniPCI slot, not MiniPCI-E, as all of my other laptops have. This is to be expected from such an old laptop, having a date code of around 2006 and probably the first model Gateway sold with Windows Vistrash back in those days.
Currently I'm using an Atheros-based card I pulled from a dead D-Link DIR-6xx model, forget which one. main chips are AR5008/5416, and is capable of N300 speeds... but I digress, I believe it to be using much more power than I could want so to keep battery usage down. I have a 12-cell battery attached that has about 6% wear on it, and it lasts roughly about 3 hours with media going, and about 4-5 if I'm not doing anything intensive.

What I'd like to know is if there's some other chipset I should be looking for aside from this that uses less power, or if there's nothing better?

I found a lot of $8 BCM43222 dual-band wireless cards on eBay that are half the height of the original card, and I've confirmed the antenna leads to reach to even the MiniPCI connector itself. it seems that people have issues with the drivers (not an issue for me at all, I'm more than competent.), but I haven't seen any remarks on power consumption. There's also the normal TP-Link cards that look the same as my AR5008 card but with a different chipset (a new revision with a pin-compatible replacement!) and not much else aside from some ar9160 chipset cards of different sizes and oversized 802.11g MIMO cards I wouldn't even breathe on to save my life.

so basically what I'm looking for is a wireless chipset, 802.11n 150 or 300Mbps, on a MiniPCI card (NOT MiniPCI-E!!), that is overall efficient while still providing moderate range and throughput capability. this also depends on the antennas used, but that's for another day. I'm also okay with cards having 3 antenna hookups, I can modify a third antenna into the laptop someplace if needed. (I've done this before with excellent results!)

Does this holy grail of MiniPCI cards exist for these poor aging laptops? Assume all my routers and normal AP's I connect to are N150 or N300, and also assume the main CPU in my laptop here is a Core 2 Duo T7200 2GHz, so I can up to 64-bit Win7 whenever I want to without issue.