NEW YORK ( TheStreet) -- The recent deals for Dell ( DELL), Heinz ( HNZ), American Airlines ( AMRPQ) and Virgin Media ( VMED) may indicate to some a return of the mega-deal, after years of post-crisis C-Suite caution.

It certainly is a fun exercise to speculate where Warren Buffett might aim Berkshire Hathaway's ( BRK.A - Get Report) M&A elephant gun, after the 'Oracle of Omaha' said in March that his failure to make a large acquisition was among his biggest 2012 disappointments.

But given a trend toward smaller mergers and buyouts by corporations and private equity firms, investors may do well to continue to focus their M&A speculation on small and mid-cap companies.

Rising valuations for corporations across the Russell 2000 Index ( RUT) and the Russell Midcap Index ( RMCC), a stabilizing economic outlook, an imperative for revenue growth and attractive financing, may continue to drive small and mid-cap deals in 2013, according to a March 4 screening of M&A targets by Citigroup analyst Scott Chronert.

Last year, M&A removed about 5% of the Russell 2000's total equity value -- $58 billion -- and helped drive the 14.6% return for the index, with a similar amount being acquired from the Russell Midcap index, according to Chonert's calculations.

"We continue constructive on the outlook for small and midcap M&A activity during 2013," Chronert wrote.

"Typically, small cap will be characterized by more deals, but with smaller size. Conversely, deal count in mid cap is typically lower, but with offsetting higher deal values," the analyst added, while noting Buffett and 3G Capital's $23 billion deal for Heinz has driven mid-cap M&A this year.

Using a screen for positive free cash flow and low debt companies, and another one for underperforming stocks and fundamentals relative to peer groups, Citigroup highlighted actuarial firm Towers Watson ( TW), media conglomerate Gannett ( CGI), payments specialist Total System Services ( TSS), home retailer Williams-Sonoma ( WSM - Get Report), American Eagle Outfitters ( AEO - Get Report) and Packaging Corporation of America ( PKG), as possible private equity buyout targets with market caps in excess of $4 billion.

The team of Citigroup analysts also see underachieving companies such as Abercrombie & Fitch ( ANF - Get Report), car parts supplier Visteon ( VC - Get Report), Allscripts Healthcare Solutions ( MDRX - Get Report), retailer Saks ( SKS), Fuel Systems Solutions ( FSYS) and gaming software maker Take-Two Interactive Software ( TTWO - Get Report), as notable small and mid-cap deal targets in 2013.

Those firms may be the target of a strategic or private equity suitor because of low valuation multiples, higher than free cash flow yields and debt levels below peer trends, according to the Citigroup analysts, who have "buy" ratings on each of the firms mentioned.

Citigroup's forecast for a steady flow of small and mid-sized deals would reflect a continued trend for private equity firms to target in the $1 billion to $5 billion range, and for corporations to look at tuck-in acquisitions rather than transformative mergers.

Even deals the size of Dell's proposed $24.4 billion takeover and a failed attempt to take Best Buy ( BBY) private indicate that private equity firms are stretched to contribute more than $1 billion in equity to a buyout, as leverage levels come down.

Despite an increased number of deals during 2012, vverall M&A activity around the world ended the year roughly flat from 2011 levels, according to data provider Dealogic.

While M&A globally came in at about $2.7 trillion -- below 2008 levels in excess of $3 trillion -- the number of deals done exceeded levels from four years ago.

Even in the absence of blockbuster mergers like Heinz or Dell, private equity firms such as Carlyle Group ( CG), banks including Goldman Sachs ( GS) and boutiques like Evercore Partners ( EVR), were hard at work last year.

So a surge in 2013 deal making may not be such an aberration from the previous year. Dealogic data show that the nearly $1 trillion in transactions in the fourth quarter of 2012 was the highest quarterly total since the same period five years earlier.

Those who expect that merger and activity will continue to rise with overall markets and the economy, may do well to focus on small and mid-cap targets given the constraints on private equity and a more cautious stance to mergers taken by boards across Corporate America.

For more on M&A trends, see what 2013's mega-deals really mean. Also see Morningstar's top 2013 M&A picks.

-- Written by Antoine Gara in New York