I'm presuming Tradelius are the agents in question. Marshall get their stock from Tradelius.
I was afraid of this kind of thing when I saw who has the agency (it once took me
two years to get a pair of hoops for a Pearl snare drum from the same crowd - after being told 6 - 8 weeks). That is one of the reasons I decided not to buy Celestion Golds (plus the local price of R4 600K each!) but rather brought in the Weber clones.
Push Marshall to get a definite date for you - if the speakers have been ordered and shipped, the agents will have the shipping documents and know the date of arrival to within a few days. If they haven't shipped yet, ask for your money back. That will either get you your money or your speakers quickly. ?
Then look at
Warehouse Speakers. I haven't used them yet, but they get a lot of love for their classic speaker clones on the US forums. Their Greenback clone is priced at $69 and they use USPS for international, which works out a lot cheaper than FedEx or the other couriers.