Previously I always built my own DAW PC systems, and every time, the PC hardware landscape had advanced so much that I had to devote a good amount of time to understanding it all before I could start building the system.
This time I decided I’d had enough and opted for a different approach - you might consider this 
I sought out a reputable handler and told him I wanted a PC that had to optimally and without issue, run Cubase 7 on Windows 7 in 64bit - even providing the HP Specs - pointing out that it cannot cost anywhere near those HP prices. I further informed him of the specific Hardware peripherie that would be attached (Controllers, Audio interface. dual screens etc.). This was the condition of the deal - if it didn’t perform to my expectations, I was not obligated to buy it. As it turned out I haven’t had a single HW related issue (touch wood )
If you have the opportunity to arrange a conditional deal like that, at a reasonable price, it might be worth thinking about!
P.S. Another form of cheap treatment for the lowest budget would be “movers blankets”. Though not ideal they might help for damping some of the main problematic reflections.