Depending on which app you are using for SMS, many of them have an option to wake the screen in the settings. Handcent offers wake screen option. It will display a popup window for quick replies, or you can touch the contact and open the full app. Check your options or look into a new app. There are many to choose from and most are better than the stock apps with far more options and features. There's bound to be one that will offer you everything you're looking for.