The stock market by virtually any measure begins the second quarter on Monday at all-time highs.
After teasing investors all last week, the S&P 500 finally closed at a record high ahead of the long holiday weekend—following the Dow Jones Industrial Average, which has been crushing its highs for awhile now.
In the first quarter, the Dow industrial average rose more than 11 percent—its best first quarter since 1998. The S&P 500's 10 percent increase and the Nasdaq Composite Index's 8 percent gain from January through March were those indexes' best first-quarter performances since 2012.
With stock mutual fund inflows starting to pick-up, many individual investors are asking: Is it too late to buy this red-hot market? "Squawk Box" enlisted some Wall Street heavyweights to help answer that question. Here are their insights: