Preparing Ubuntu 10.04 new install - 32 or 64 bit? Please suggest.

[Juan R. de Silva]

My PSU smoked out burning an old Asus P4PE motherboard aw well, thus 
effectively invalidating the rest of the system components, otherwise 
still functioning.

So, I had to configure myself a brand new system as follows:

- Intel Core i5 2500K Quad Core Unlocked Processor LGA1155 3.3GHZ Sandy 
Bridge 6MB
- ASUS P8P67 ATX P67 LGA1155 DDR3 2PCI-E16 2PCI-E1 3PCI USB3.0 Sandy 
Bridge B3 Motherboard
- G.SKILL Ripjaws X F3-12800CL9D-8GBXL 8GB 2X4GB DDR3-1600 CL9-9-9-24 
Memory
- Western Digital Caviar Black 640GB SATA3 6GB/S 7200RPM 64MB Cache 3.5IN 
Dual Proc Hard Drive
- Sapphire Radeon HD 5570 650MHZ 1Gb 1.8GHZ DDR3 PCI-E VGA DVI HDMI Low 
Profile Video Card

Having until now and old system running Intel P4 1.4 GHz I've never been 
concerned with 32 vs. 64 bit dilemma, and now I am.

I'm going to install Ubuntu 10.04. When I get to the Ubuntu Download page 
and selecte the desired version I am offered by default "32-bit 
(recommended)" option.

What would you suggest - 32 or 64 bit? My new hardware suggest 64 bit.  
But would I run into any problems going this way: performance, 
applications support/availability, etc.? Why Ubuntu folks recommend 32 
bit instead of 64 bit version?

Thanks.