You can just put a cheap i5 2400 and you will be golden for a bit at least https://www.aliexpress.com/item/Intel-Xeon-E3-1220-3-1GHz-5-GT-s-Quad-Core-CPU-Processor-SR00F-LGA1155/32656897326.html?spm=2114.search0302.3.37.656310d7CEsBWE&ws_ab_test=searchweb0_0,searchweb201602_0_10130_10152_10151_10139_10618_10059_10696_10534_10313_10084_100031_10083_10547_10624_10623_10307_10548_443_10341_10065_10340_10068_10343_10342_10103_10620_10344_10622_10621,searchweb201603_0,ppcSwitch_0&algo_pvid=abec2232-02ec-46eb-9049-c0f4b2cfb361&algo_expid=abec2232-02ec-46eb-9049-c0f4b2cfb361-4