The Asus Designo MX34VQ is the most affordable 3440 x 1440 ultrawide display you can get with a 100Hz refresh rate. And it doesn't skimp on features to hit this price point: the monitor comes with a Qi wireless charging base, decent Harmon Kardon speakers and support for FreeSync.
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips