Hardware estimation

Hi,

I am a first timer in this forum. We have  an application  using
Postgre Database with a considerable growth expected for the next
year. We are facing some dificulties to estimate the equipment we´ll
need  and I would like to exchange ideas about:

- hardware estimation
- performance concerns

 with anyone that faced Postgre applications with more than 150Gb.

I am talking about a database that will achieve:

- 200Gb total space
- 2 major space cosuming tables (400 million and 50 million tuples)
- major system process - batch process reading from and writing to
text files (telephony records) - aprox 2 million records processed
(read or written every day)

Operating System : Linux

Equipment we are planning:
- IBM xSeries 255 4 Intel Xeon 1.5GHz, MP, 512KB Cache, 2GB RAM,
External Storage System(IBM SSA)

Thanks in advance

Vidal Zebulum
vzebulum@yahoo.com.br