Well, I have the Dell T5400 among other self build systems, and the problem I often find with pre build systems is the lack of harddrive bays for storage, and it seems to me that you only get a few bays in this one too.
There is a similar system in our PPBM5 Benchmark. Dual E5-2620, 16 GB memory, Quadro 4000, SSD, 2x HDD in raid0. That system scores around median. The Dell will not be any faster, where - if you take the price into consideration - it should do much better, around twice faster.
The problems with this Dell system are the low clock speed of the CPU's, the limited amount of RAM, the Tesla card that only costs a lot but does not deliver, the disk configuration, the very limited SATA ports, the limited size of the case, the crippled BIOS of Dell, the lack of overclockability, the limited PSU. The only thing in favor of it is - at least from the suppliers point of view - the ugly price.
Your own system is much better and faster for a more attractive price. I have yet to see a Maximus configuration that comes close to a GTX 680, despite the extravagant price.
Thank you Harm for these explainations, I'm quite happy I took the "home built" route rather than paying for a so called specific engineering and integration...
While that particular configuration may not be optimal, as Harm mentioned, it's fairly easy to configure one that is better suited for Adobe apps. People who have actually used Tier 1 systems, usually appreciate the design and engineering. T5600, for instance, is rackmountable, has a standard 3-year on-site warranty, externally accessible drive bays, dedicated memory cooling, case handles among other things separating it from DIY designs.
In addition, T5600 is expandable to 128GB, more than any single socket DIY system.
Most importantly, you don't have to buy one of Dell's Adobe configurations. A popular approach is to get a fairly bare configuration with the right CPU, and then add 3rd party options to tune it perfectly for Adobe apps: storage (an SSD, several drives for a media volume), graphics (GTX-670 or 680), 3rd party RAM. You could do it yourself or find an integrator who specialized in Tier 1 systems.
T5600 is however indeed limited in the number of drive bays and SATA ports, and will work the best with external storage. Dell T7600 is much more expandable; HP's Z820 and Z620 both have more bays and up to 14 on-board SATA and SAS ports, with up to 12 drives internally.
Purely on cost, DIY systems always win. Where design, engineering, serviceability, warranty options, support come in play, Tier 1 systems often have an upper hand. The reason I think that, is because as a systems integrator, I've been selling and supporting both custom and Tier 1 based editing systems for the better part of the last 20 years.