Sonicwall Wireless Expansion Question Anyone read...

I have a Sonicwall TZ 170 Wireless up in the ceiling tiles of an office building. Most of the computers in the surrounding area get great reception. Around the edge of the building reception is poor and data traffic is slow to none. Anyone know what I can try before buying a 500 dollar Sonic Point (signal repeaters or better pci wireless cards). Much help appreciated...
Thanks,

Justin Curtis