Upgrader,
Given the specification and the general good build quality and high reliability, the HP z400 is a very good value, keeping in mind the immediate need for an operating system, the eventual great usefulness of both more RAM (I'd have a minimum or of 8, but 16 is better to allow several simultaneous applications, and the great desirability of a better GPU and possibly a faster CPU.
With an OS added, you would have a good system to learn the graphics applications you mentioned. Effects processing in 2D and rendering do require a fast CPU and healthy GPU, so beyond a certain file size and complexity, you may yearn to be an upgrader. Most Adobe products are CUDA accelerated so an Nvidia graphics card will help. Fortunately, if you believe you will be staying in the 2D realm, you can use an older Quadro - the FX3800 now about $60-80 is excellent in 2D, or indeed a good GTX like a 650 which will be very good in 3D as well. In all cases, check each application you think you might be interested in and check the manufacturers' recommendations. If the application stresses OpenGL, a GTX will be more useful, if you want the highest anti-aliasing, viewport, and error correction, it's a Quadro. When buying a workstation with a Xeon and ECC RAM, and running workstation programs, I would usually carry on through and buy a Quadro.
The z400 is using an LGA1366 CPU at 2.8GHz, which is acceptable in your intended use, but a 3.2 or better wouldn't hurt. If you want, that system can use one of the best Xeon's ever made, the 6-core X5680 at 3.33 / 3.6GHz, but those are still very expensive ($900+). There are several LGA1366 CPUs that are not as terribly expansive used if you decide to upgrade.
I really don't know Lenovo workstations, but I have had a couple of Dell Precisions and the Dell T3500 can be very good. They are generally a bit better performing than the HP and in my view have a better build quality than HP. They are also typically noticeably more expensive than HP's used.
Buying a used workstation can be a bit tricky as adding an OS and better video card can quickly make the $200 system a $450 system and for $500 you can find >
http://www.ebay.com/itm/Dell-Precision-T7500-Xeon-Quad-Core-3-47GHz-12-GB-272-GB-DVDRW-Windows-7-/310836319424?pt=Desktop_PCs&hash=item485f49d4c0
> which is (a completed sale) T7500 with a 4-core at 3.47GHz, 12GB RAM, and Win 7 Professional operating system. This would need a better GPU as well- say a $150 FX4800 (1.5GB) but this system could be expanded to run 2X 6-core CPU's, 192GB RAM, and has a 1000W PSU, so it's usefulness without changing systems could last for two or three years longer, be worth more when finished with it, and in the end- the system cost per year is less. I bought a used Precision T5400 for $500 in 2010, spent about $500 on it- (Win7 Ult 64, 2nd CPU, added 12GB RAM to have 16, and a Quadro FX4800), used it for almost 4 years and it is worth today about $800-900 which I think of as having a quite fast 8-core workstation for $50/year.
It is complicated, but if you're in a hurry and funds are very limited, I 'd say get the z400, add Win 7 Professional 64 (+$140), and plan on buying soon (next two months) something like a good used 1GB Quadro- either a K600 or possibly a Quadro 2000 (+$80 to +200). When thinking about a replacement GPU, check the way your applications work and consider whether 3D is in your future.
Cheers,
BambiBoom
1. 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 // Windows 7 Professional 64 > AutoCad, Revit, 3DS, Inventor Pro, Solidworks, Adobe CS MC, Corel Technical Design, Sketchup Pro WordP Office , MS Office Pro [Passmark system rating = 3815, 2D= 712 / 3D=2044]
2. Dell Precision T5400 (2008) > 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 > AutoCad, Revit, Solidworks, Sketchup Pro, Corel Technical Designer, Adobe CS MC, WordP Office, MS Office Pro (Passmark system rating = 1859, 2D= 512 / 3D=1097)