The trick is that one device in any case to escape do not succeed. You can, of course, to start is to take Nexusone as the basic model, but the problem (in the literal sense of the word) of Android is that the screen resolution and the performance of the devices are too different! As a minimum, the kit will have to either get another Tattoo (if you plan to support older OS versions) or it WildFire — for QVGA resolution and high performance can bring many surprises. Different UI from different manufacturers is also able to "spoil life", so good, need Samsung, and Acer.
Clearly, the more devices, the more you need testers and the more you need money, these all the device to buy... Yes, this is the main problem of Android... But, on the other hand, there are also community?! Beta testing with the distribution of soft — quite lively scheme. Many developers even at the highest level it is used... So not so sad!