Building cell phone booster systems come in all different sizes and for many different purposes.  Sometimes a system is needed for more than a single room or two.  Most of the time when signal is required in 2,000 to 3,000 square feet, a 65dB amplifier with low loss coax is required.

There are single band and dual band 65dB cell signal boosters on the market.  Sprint and T-Mobile use 1900MHz, while Verizon and AT&T are usually considered dual-band carriers that use both 800MHz and 1900MHz.  I would always get a dual-band system.  This allows you the freedom to switch carriers and also protects you if your carrier changes frequency in your area for any reason.  Dual-band protects your investment. 

When doing several thousand square feet, it is best to use a low loss coax equivalent to LMR400.  Coax like RG6, RG58 and LMR240 have more than double the loss of LMR400.  Loss is important, the more loss in the coax, the less broadcast you get from the amplifier.  When doing a small building or home, you need all the broadcast you can get. 

It is always best to do business with a company that has experiance in selecting and designing a system for your specific situation.  Many companies will sell parts, but they lack the knowledge to accurately design a system that will deliver what you need or expect.  Make sure the company you do business has the proper investment in inventory, knowledge to help you design the system and technical support to answer any questions during the implementation process.