Keeping a balance between performance and complexity is a well-known dilemma in large-scale multiple antenna systems. In this paper, the system complexity and the outage probability are evaluated for a large-scale multiple-input-single-output (MISO) system. To obtain the explicit analysis results, the cumulative distribution function (CDF) of the sum of the K-largest order statistics of N independent exponential random variables is first developed. Then the complexity and the outage performance are evaluated with perfect and imperfect channel statement information (CSI). The asymptotic analysis are conducted to give some insights for the design of such a system. Finally, numerical results are provided to verify the accuracy of the developed theoretic results, and show that it is not necessary to always use all antennas to transmit.