Longer range Wireless

We currently have a linksys router [wrx400 with MIMO] and a matching card installed at a location.[yes, I know, linksys sucks] The system with the wireless card is in another building about 150ft from the router. The reason we bought that setup was because of their claim that it extends the range up to 300ft. Plenty of range, would you say?

The problem is that the system keeps on dropping the signal. We did a netstumbler test and it sitting at about 90dB, which is not good enough.

Linksys tech support in bumfakistan claims that 150ft is OUT of the range capabilities of their router. wtf?

Does any of you know of a better [read: longer effective range] wireless package?

Is a larger antennae + card an option that you have tried so it picks up the signal from the router better?? Or if the antennae on your Linksys is detachable, then you could buy a more powerful one??!!
For example: http://www.radiolabs.com/products/wireless/networking/long-range-mobile-wifi-kit.php?PHPSESSID=4baf2cd f8763e3d3240230898db69697

Guess another option would be a wireless bridge...

Very Good link to DSL Reports which has info you seem to be aware of, but scroll down to bottom and follow those links to some forums about similar issues like yours:
http://www.dslreports.com/faq/11828

In the DSL Reports link there was this:
Q: How Can I Boost My Range? (#10944)
A: Try to make the most of what you have before spending a lot of time or money on signal boosters, repeaters or external antennae.

* Change the position of the devices to see if you can get a better signal.
* Adjust the position of the antenna on either the router of the client to optimize the signal.
* Change the channel on the wireless router or access point in an attempt to avoid sources of interference.
* Try an inexpensive reflector to focus the signal in the desired direction. Some excellent templates and instructions:

All kinds of good shit here!

http://www.radiolabs.com/