So, if you have only 300 bucks to spend, this is the card I'd be looking at. Anything less than this, at 1440p, unless you are willing to seriously reduce settings, will be disappointing. Save a little more money, get a card that can actually GIVE you at least 60fps at high or ultra settings at 1440p. The 1660 ti is not that card.
PCPartPicker Part List
Video Card: Sapphire Radeon RX 5700 8 GB PULSE Video Card ($359.99 @ Newegg)
Total: $359.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-11-05 17:01 EST-0500
Better even, would be to save a bit more and go with an RTX 2070 or RX 5700XT, but obviously those require a significantly higher investment while the RX 5700 only requires a minimally higher one.
More important might be what power supply you have. Any of these cards is going to require a high quality, capable unit. What is the exact model of your current power supply?