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If you're not in a huge rush, I'd suggest you skip flying, and take the train. Well, train + train + ferry. That way, you'll have the computer parts and monitor with you at all times, can keep an eye on them, can ensure that no baggage handlers throw them about it.
Booked a little bit in advance, it's actually not that expensive either, especially when you factor in that there's no checked / oversized luggage to pay for!
First up, you'll want to take the Eurostar to London. Journey time is around 2 hours, and tickets cost from about €50 (they go up nearer departure). If you're not starting your journey in Brussels, you'll want to book an Any Belgian Station ticket. That adds about €10 to a one-way ticket, but will give you a ticket from anywhere in Belgium on the train to Brussels to connect with your Eurostar. More details on the Seat61 Belgium page
Eurostar officially allow 2 large items plus one small one, of any weight that you yourself can carry. Unofficially, you can often manage a little more than that, but they may be stricter on the rules if the train is very busy.
The Eurostar will drop you at St Pancras station. You need to get to Euston station, which is quite close. See this question on the quickest way between the two. (St Pancras is right next to Kings Cross, on the Euston side)
From Euston, there are direct trains to Holyhead, and you can buy combined train+ferry tickets. These cost a whopping £38 one way! See the Seat61 Ireland page for details. It takes about 4 hours to Holyhead, then another 2-3 to Ireland, depending on if you get the fast or the slow ferry. There's some very picturesque scenery on the way.
On arrival in Dublin, you can take a bus from the ferry terminal, or probably you'd want a taxi given how much stuff you'll have
Not quick, but with the Eurostar booked in advance you can do it for under £100!