i'll try to help -

Dell 24 incher - go for it - Full HD goodness, compliments the 4870

inverter - do you need a inverter or UPS? I use a Sukam non sinewave 1400VA inverter with 2X 150A Exide tubular batteries.
If you are not looking for an inverter just get a branded 1KVA UPS

MX5021 & Logitech Z 2300 - i presume the Z2300 is a bit boomy. MX5021 is a much better buy imo but with a recent quality issues that i have seen here i am confused.