Why is it that coders don't ever convert a PSD using the right spacing?

You just add/edit your styles in the browser and copy it to your css file once it's correct.

You really ought to try the LiveReload plugin for Chrome or FF. Then you can edit your CSS in Sublime instead and see the changes in real time in your browser.

Use a tool like LiveReload or similar and all your HTML/CSS changes show up in real time as you make and save them in your text editor (Sublime Text for example). Put your text editor on one screen and your website in a browser on another and you're good to go.
 


You really ought to try the LiveReload plugin for Chrome or FF. Then you can edit your CSS in Sublime instead and see the changes in real time in your browser.

Editing via Firebug is as live as it can get though? Not sure why I would want my entire page to reload every time I change a pixel setting when I can watch the element nudge pixel by pixel with the arrow keys and then just copy and paste that code block into my css file and move on.

Including SASS and SCSS

I'm not a big fan of anything except pure css mainly because I'm stubborn, but that would be a compelling reason to use livereload I suppose.
 
If you ever need precision HTML5/CSS in the future - hit me up. I'll even do it before charging you and you don't like - you don't pay. Surprisingly, I thoroughly enjoy slicing and optimizing the front end designs. Use sprites to minimize requests. Minify all assets where applicable. Compress images real well with various tools and so on. I can really make you page light and effective, yet replicating original PSD as close as it's possible with HTML and CSS. I'll also tests it in all A browsers and some popular B browsers as well.