Server definition

No. Really. It does.

How often are you selecting records from this database? How complex are your queries & stored procs?

That helps with the memory/cpu requirements.

How wide are your tables? That determines how many rows can be stored on your hard drive.

In general, figure out how much data you plan on storing. Then from there, you can determine how much hard drive space to carry in the box.

The CPU/Memory and whether or not to go RAID depends on the usage pattern, but the best advice is to get as much CPU/Memory as your budget allows, and get RAID & Multiple CPUs if at all possible.

Now if this is just a simple reporting server, you may not have high CPU/Memory needs, but a lot of hard drive space requirements.
An OLTP-style server is going to need the opposite specs (lots of CPU/Memory power and not as much hard drive space).

Your best bet of all is to not post for free advice on a forum, but talk to an actual DBA, who can give better advice than what you could ever get without your own background on the topic.

Remember, you get what you pay for.

Hope this helps,
Steve