Yeah, the K sku would be a complete waste. In later eras, the K typically had higher base/boost clocks vs the Non-K, but the 2600 and 2600K are clocked exactly the same.
pick up an r7 240 and call it a day.
I don't know what the question is, but the R7 240 is extremely unlikely to be the answer.
From what I can see, a used 240 sells for between $25-$40.
At that pricepoint, something liek a GTX 750,
750TI,
760, 950 or (maybe) a
960 might be achievable
On the AMD side of things,
RX550, 460,
560, or something older like a
270/270X
all of these cards, while not necessarily the latest & greatest, are orders of magnitude better than an R7 240.