I want a new monitor

I am considering whether I should buy a new Mac and a monitor for it. Now I use a laptop at the office. However, its screen is a little small for my work. So I want to do my work on dual monitor. The monitor I want is about $350. I think it’s not so expensive for a high-quality Japanese monitor. But I built a house with a loan which continues for more than thirty years. So it’s a hard decision for me to buy it.