VBR, the Vanguard Small-Cap Value fund/ETF, is a great investment option, IMO. It's big for a small-cap fund, though, so it's investment universe goes up into smaller mid-cap stocks as well.

Still, it has low turnover, low fees, and gives you great diversified exposure to US small cap value along with lower end mid-cap value.

It's more volatile than the S&P 500, but, IMO, this is one where you do expect better long term returns for your additional volatility. There is a history of small-cap value outperforming the S&P 500, and a reason to believe that should continue, given behavioral economics and valuation grounds. And in particular, IINM, valuation of small cap value stocks is even better compared to the SP500 than is usually the case, purely on a relative basis, see earlier posts on this board by me and Manlobbi.