In terms of resolution, you are golden (full HD is plenty for 27 inch, I have a 17 inch laptop with 1080p, a 27 inch 1080p ips monitor and a 50 inch plasma 1080p TV. All of them look great in 1080p, the plasma the best due to color accuracy and black levels).
Pixel density is not something objective, its subjective, so no one can tell you what you should be aiming at (there are people with smartphones who want 4k resolutions, go figure).
In terms of monitors, I know not much, but what I do know is that prices go to the roof if you want all the bells and whistles (size, high resolution, ips panel, 144hz, G-sync/freesync... it all adds to the price).
I went for a 27MP65HQ-P from LG (IPS, 1080p, 60hz, no g-sync/freesync) because unless I get OLED monitors, the are all looking a bit bad in terms of video quality compared to the plasma so no point in overspending (at least for me).
I would also recommend checking tftcentral (http://www.tftcentral.co.uk/articles/flicker_free_database.htm) especially to make sure I pick a flicker free monitor.