Building a new desktop pc

[FRESHWATER65]

I am looking for guidance on building a new desktop computer from scratch.
Current computer is being handed over to my son and I want to have a shot at building my own. Will turn 68 yrs in three months and this is something I want to do before I am past it or senile (whichever comes first)!
This is what the current computer has:
Processor: Intel(R) Celeron(R) CPU 3.06GHz
Clock Speed: 3066 MHz
Motherboard: MSI G41M-P28 (MS-7592)
BIOS :V26.5 - Default System BIOS (20110120)
System RAM: 4061 MB (532 MHz)
Graphics card: Intel(R) G41 Express Chipset
Hard drive(s): 500GB Hitachi HDS721050CLA362 ATA Device
Optical drive(s): TSSTcorp CDDVDW SH-S223C ATA Device
Sound card(s): High Definition Audio Device
Operating system: Microsoft Windows 7 Home Premium SP1 (64-bit)
Monitor: Generic PnP Monitor
Graphics card specs:
Model: Intel(R) G41 Express Chipset
RAM: 1894346752 bytes (1806.59MB)
Resolution: 1440x900-pixels / 32-bit colour @ 59Hz
Max refresh: 75Hz
Driver: igdumd64.dll,igd10umd64.dll,igdumdx32,igd10umd32
Version (Date): 8.15.10.2555 (20111013)
Video DAC: Internal
WHAT THE NEW COMPUTER WILL BE USED FOR.
General home office work and down loading information from the Internet.
Maintaining some large spread sheets and data bases. Currently have two spread sheets with 35,000+ records each and these are growing at the rate of an extra 30,000 records annually. A data base collects information off these spread sheets!
Playing music; watching videos; web surfing.
No gaming or video editing or movie making.
The spread sheets are slow to load and slow to sort.
THESE ARE MY IDEAS ON WHAT I NEED AND MY BUDGET IS MAXIMUM $600 BUT PREFERABLY LESS AS I WILL HAVE TO BUY A NEW OS.
Also I live in Australia and will most likely buy components here.
A good quality mother board and CPU. Want to stick to Intel and thinking Core i3. At least 6 USB ports but more would be better.
Integrated sound & graphics
8 GB RAM
1TB hard disk
Full tower ATX case
DVD drive
I already have speakers, monitor, key board, mouse, printers.
In a nut shell I am looking for something better than I can buy as an off the shelf, ready built from a computer store. Something with a bit of grunt that won't break the bank.

[glc]

Mwave.com.au - Gigabyte GZ-PD-PLUS Black Mid Tower Case No PSU

Mwave.com.au - Antec VP Series VP450P 450W Power Supply

Mwave.com.au - ASUS P8Z77-M Motherboard

Mwave.com.au - Intel Core i5 3470 4-Core 3rd Gen Processor

Mwave.com.au - Corsair Vengeance LP 8GB DDR3 RAM CML8GX3M2A1600C9

Mwave.com.au - Western Digital WD Black WD1002FAEX 3.5" 1TB SATA 6.0Gb/s Hard Drive

Mwave.com.au - Lite-On IHAS120 20x Internal Super All Write DVD Burner Drive

[FRESHWATER65]

Thanks for your most helpful reply.