Besides the graphic card it seems your cpu could be causing the frame drops. The more bots you have, the more resources are being used to power the games AI, so if you're frame rate decreases there, it's because of your cpu.
If you've got viruses, get a good anti-virus and clean your computer out.
Your computer keeps writing files to disk, and to save time it writes them to the first available space. So over time your files get fragmented, making your computer run slowly as to open 1 one, the computers got to read it off 10 different locations on your disk. Defragmenting your hard drive will boost performance. While playing games, your computer will read files off the disk, so that may be part of the reason why you're experiencing slow downs.
Your psus input in 230v, check what the output is, it'll be in watts.
The benefits of assembling your own pc:
1) you'll get something that meets your needs.
2)a branded pc will usually carry a 1 year warranty, whereas if you buy quality parts for your own computer, you'll get between 3-5 yrs warranty per part.
3)with a branded pc you'll get something that's well put together, and that'll last you well till the warranty expires. It may last you longer, but if you buy good quality stuff, you'll probably get a longer life on your assembled pc.
4)if you want to upgrade your branded pc, you'll have to call the manufacturer or risk voiding your warranty.
5)while upgrading you may need to change multiple parts in order to change just one. for example, if you need to add a more modern graphic card, you may have to upgrade the power supply before you can put in a new card.
6)you won't get software updates for your motherboard easily, so if you want to upgrade your cpu later, you may not be able to even if your system should technically support it.
If you buy a low-end branded pc, even from Dell, it'll cost less than what you pay to build your own system, if you only choose quality parts.
You can also buy cheap stuff and make a system cheaper than any company, but that's not advisable.
Buy good quality components, know what your needs are, and your computer will last you atleast 3 years without any trouble, and should still be performing acceptably at the end of that period. Just make sure you know what you're doing.
