What is the maximum upgrade for Dell Inc. Precision T3600?

Overview

Computer model: Dell Inc. Precision T3600

Operating system: Microsoft Windows 10 Pro (10.0, Build 19045)

Processor: Intel(R) Xeon(R) CPU E5-1620 0 @ 3.60GHz 4/8

Motherboard: Dell Inc. 08HPGT

RAM: 32 GB

Hard disk1: DELL PERC H310 SCSI Disk Device (237.9 GB/Fixed hard disk media)

Hard disk2: StoreJet SCSI Disk Device (232.9 GB/External hard disk media)

Graphics card: NVIDIA Quadro 4000 (2 GB)

Power- 635w

(I need to use for basic Lumion rendering/ autocad architectural/basic gaming) 

Suggest an upgrade which you have tried not just Googled, even I could do that, Karl . Thanks.