Mishandled: If your monitor is good - or you can live with it - consider just getting a new system unit for this year. Then the monitor next year?
I try and upgrade something every year. Last year it was the system, this year it will be some significant bolt-in expansion devices for it. The monitor is three years old and doing fine.
Nowadays, if you get a standard system box, anything will fit inside it and most folks that know that onions, can fix it. Standardisation has brought some benefits, we won't waste time on the non-benefits!