I edited my old post with link to the benchmarks. This is what i recommend:
NCIX.com - Buy Intel Core i5 2500K Quad Core Unlocked Processor LGA1155 3.3GHZ Sandy Bridge 6MB - Intel - BX80623I52500K - in Canada
Price match this to NCIX
Agile Electronics - Buy Mfgs Part-#:GA-P67A-D3-B3 online in Canada
Re-use old ram or tell your son to pick it up himself soon. Honestly the i5 2500k is heads and shoulders above everyon else. Also I recommmend overclocking even though you said he wouldn't. It will literally take 5 minutes. Up the fsb up the multiplier run a test see if it's stable. 4.0 ghz on stock cooler easy with almost no temperature changes.
These CPU's are pretty sweet.
Alternatively if we stick to absolutely no overclocking.
NCIX.com - Buy Intel Core i5 2500 Quad Core Processor LGA1155 3.3GHZ Sandy Bridge 6MB - Intel - BX80623I52500 - in Canada Gigabyte H67A-UD3H-B3 ATX LGA1155 H67 DDR3 2PCI-E1 3PCI 1PCI-E16 CrossFireX SATA3 USB3.0 Motherboard - DirectCanada
The only problem is that you need to go up to $130 for a mobo to get ATX sized H67.
This means you are much better off budget wise to go with the P67 chipset anyways.
If you absolutely need ram check this out.
Buy The AMD Phenom II X6 925 Processor 3.2Mhz 125W AM3 Processor at Vuugo. Speak to one of our Customer Service Representatives for more information! Gigabyte 890GPA-UD3H 890GX AM3 ATX DDR3 2PCI-E 2PCI SATA3 USB3.0 HDMI GBLAN CrossFireX Motherboard - DirectCanada
Ram: I know ideally you want 8 gb or more for CS5 but it's not in the budget. gigabyte said they would allow you to put bulldozer chips in this mobo which is why I picked it otherwise you could go less and pick up more ram.
NCIX.com - Buy G.SKILL F3-12800CL9D-4GBRL Ripjaws PC3-12800 4GB 2X2GB DDR3-1600 CL9-9-9-24 Core i5 1.5V Memory Kit - G.Skill - F3-12800CL9D-4GBRL - in Canada
pick up another one when you upgrade.