toneenthrall,
The Inspiron 620 is a good and reliable system, but will be somewhat limited in performance, and value- perhaps £250, so I would suggest not overspending on moderate improvements.
You can use >
CPU > Intel Core i5-2500K Sandy Bridge 3.3GHz (3.7GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 3000 BX80623I52500K
> which is a very good CPU from the 2nd generation. The thing is, your current CPU is 3.0GHz (3.3GHz Turbo Boost) and to use the i5-2500 you'd have to find a used one. A quick look at eBay UK suggests this would cost in the neighborhood- sorry
neighbourhood of £130.00. In my view, the 300-400MHz increase in speed is on the edge of not being worth the cost due to the other limitations.
The increase in RAM (a slots, 1333 speed) to the maximum of 8GB is worthwhile to be able to run multiple applications. You might check the current RAM configuration in the event it has 2 X 2GB modules in which case you would have to replace both. If it has 1 X 4GB, then you can add another 1 X 4. I'd suggest that the added RAM be the exact model number of the other one- look for RAM on ebay specifically listed as coming out of an Inspiron 620.
For a graphics card, perhaps a GTX 650 2GB, which can be about £60-100 depending on used or new, from the US (cheaper but higher post and import fees) or from the UK.
Depending on your ultimate use, and degree of fuss allowed, but if you need /expect quite high performance, especially in gaming, you may be better off selling the Inspiron 620 and adding the £500 to have something already with a faster CPU (such as i7-3770), more RAM at a higher speed (such as 1600), and fast graphics card. One disadvantage of the i5 is that it is not hyperthreading- which is an advantage in programmes such as Photoshop. Have a look at >
http://www.ebay.co.uk/itm/Dell-XPS-8500-2-TB-Intel-Core...
> which is a completed listing for an Dell XPS, with an i7-3770, 8GB RAM, 2TB HD, and Radeon 7770 (1GB) card. The video card in this example is nothing special, but the system at £475 means you could look for a good GTX 650 (or 650ti) 2GB and something like this should be a good all-rounder and be useful for years longer.
Of course, it is less fuss to add some RAM and a better video card to the Inspiron, but to avoid overspending I would not change the CPU.
Cheers,
BambiBoom
HP z420 (2013) > Xeon E5-1620 quad core @ 3.6 / 3.8GHz > 24GB ECC 1600 RAM > Quadro 4000 (2GB)> Samsung 840 SSD 250GB /Western Digital WD1003FZEX 1TB> M-Audio 192 sound card > AE3000 USB WiFi // HP 2711X, 27" 1920 X 1080 // Windows 7 Ultimate 64 > Autodesk Building Design Suite, Inventor Pro, Solidworks, Adobe CS MC, Corel Technical Design Sketchup Pro, WordP Office, MS Office Pro [Passmark system rating
= 3815, 2D= 760 / 3D=2044]
Dell Precision T5400 (2009) > 2X Xeon X5460 quad core @3.16GHz > 16GB ECC 667> Quadro FX 4800 (1.5GB) > WD RE4 500GB / Seagate Barracuda 500GB > M-Audio 2496 Sound Card > Linksys 600N WiFi > Windows 7 Ultimate 64-bit > HP 2711x 27" 1920 x 1080 > (earlier versions) AutoCad, Revit, Solidworks, Sketchup Pro, Corel Technical Designer, Adobe CS MC, WordP Office, MS Office Pro [Passmark system rating = 1859, 2D= 512 / 3D=1097]